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Signals often covary with physiological and behavioural traits to form an axis of integrated phenotypic variation associated with reproductive performance. This pattern of phenotypic integration could result from intrinsic between-individual differences that are causally related to signal production, physiology and behaviour. Alternatively, signal expression itself might generate feedback between physiology, behaviour and the experienced social environment, resulting in an integrated phenotype. We manipulated the plumage of female tree swallows, Tachycineta bicolor, to decouple the expression of a social signal from any pre-existing behavioural or physiological differences. We collected a time series of physiological samples, monitored nestbox visiting patterns with a sensor network and tracked reproductive performance. Relative to sham controls, dulled females' nests were visited more by conspecific females and less by males. Dulled females subsequently made fewer trips to other nestboxes and increased nestling provisioning. However, these changes in nestbox visiting patterns depended on both the focal female's pretreatment plumage and on the breeding stage. These differences resulted in an altered internal microbiome and glucose levels and, ultimately, dulled females produced more offspring. Moreover, dulled females produced larger clutches than control females in the year after the manipulation. Thus, signal variation alone – independent from any pre-existing differences – had a sustained causal effect on a suite of integrated traits. This finding suggests that dynamic feedback may play a role in coordinating an integrated signalling phenotype.

The Keller-Segel-Stokes type system with indirect signal production, as given by { n t + u ⋅ ∇ n = Δ n − ∇ ⋅ ( n S ( n ) ∇ v ) , x ∈ Ω , t > 0 , v t + u ⋅ ∇ v = Δ v − v + w , x ∈ Ω , t > 0 , w t + u ⋅ ∇ w = Δ w − w + n , x ∈ Ω , t > 0 , u t + ∇ P = Δ u + n ∇ ϕ , ∇ ⋅ u = 0 , x ∈ Ω , t > 0 , is considered in a bounded domain Ω ⊂ R N , N ∈ { 2 , 3 } , with smooth boundary, where ϕ ∈ C 2 ( Ω ‾ ) and S ∈ C 2 ( [ 0 , ∞ ) ) . Under the assumption that there exist C S > 0 and α ≥ 0 such that | S ( n ) | ≤ C S ( n + 1 ) − α for all n ≥ 0 , it is shown that for all suitably regular initial data an associated initial-boundary value problem possesses a globally defined bounded classical solution in the case N = 2 . In the case of N = 3 , the conclusion is also true provided α > 1 9 .

As a kind of convenient, fast, and online analysis technology, point-of-care testing (POCT) technology has been widely used in disease diagnosis, health management, environmental monitoring and emergency response analysis. To date, it is a hot spot to develop novel strategy for the detection of various targets based on the simple, rapid and sensitive signal readout and different signal production, transfer and amplification strategies in the field of POCT. The introduction of some nanozymes and functionalized nanomaterials with special catalytic properties further accelerate the application of simple signal readout such as color, temperature, pressure, weight and distance, which greatly promotes the development of simple readout-based POCT methods, and expands the analytical applications of such methods. In this paper, we summarized the principles, classifications, and the applications of these emerging POCT methods for the analysis of life-related targets and reviewed their current challenges and future application prospects.

This paper deals with a fully parabolic inter-species chemotaxis-competition system with indirect signal production \begin{document}$ \begin{eqnarray*} \label{1a} \left\{ \begin{split}{} u'>under zero Neumann boundary conditions in a smooth bounded domain \begin{document}$ \Omega\subset \mathbb{R}^{N} $\end{document} ( \begin{document}$ N\geq 1 $\end{document} ), where \begin{document}$ d_{u}>0, d_{v}>0 $\end{document} and \begin{document}$ d_{w}>0 $\end{document} are the diffusion coefficients, \begin{document}$ \chi\in \mathbb{R} $\end{document} is the chemotactic coefficient, \begin{document}$ \mu_{1}>0 $\end{document} and \begin{document}$ \mu_{2}>0 $\end{document} are the population growth rates, \begin{document}$ a_{1}>0, a_{2}>0 $\end{document} denote the strength coefficients of competition, and \begin{document}$ \lambda $\end{document} and \begin{document}$ \alpha $\end{document} describe the rates of signal degradation and production, respectively. Global boundedness of solutions to the above system with \begin{document}$ \chi>0 $\end{document} was established by Tello and Wrzosek in [J. Math. Anal. Appl. 459 (2018) 1233-1250]. The main purpose of the paper is further to give the long-time asymptotic behavior of global bounded solutions, which could not be derived in the previous work.

In this work, we consider the quasilinear attraction–repulsion chemotaxis model with nonlinear signal production and logistic-type source. We present the global existence of classical solutions under appropriate regularity assumptions on the initial data. In addition, the asymptotic behavior of the solutions is studied, and our results generalize and improve some well-known results in the literature.

An important goal of synthetic biology is to build biosensors and circuits with well-defined input-output relationships that operate at speeds found in natural biological systems. However, for molecular computation, most commonly used genetic circuit elements typically involve several steps from input detection to output signal production: transcription, translation, and post-translational modifications. These multiple steps together require up to several hours to respond to a single stimulus, and this limits the overall speed and complexity of genetic circuits. To address this gap, molecular frameworks that rely exclusively on post-translational steps to realize reaction networks that can process inputs at a time scale of seconds to minutes have been proposed. Here, we build mathematical models of fast biosensors capable of producing Boolean logic functionality. We employ protease-based chemical and light-induced switches, investigate their operation, and provide selection guidelines for their use as on-off switches. As a proof of concept, we implement a rapamycin-induced switch

This paper deals with a two-chemical reaction type Keller-Segel system coupled with incompressible viscous fluid equations which models the dynamics of cells in fluid in a two dimensional bounded domain $\varOmega $ $$ \left\{ \textstyle\begin{array}{l} \partial _{t}n+\mathbf {u}\cdot \nabla n = \Delta n - \nabla \cdot \bigl(n\chi(n,v,w,x)\nabla v\bigr), \\ \partial _{t}v+\mathbf {u}\cdot \nabla v= \Delta v -v + w, \\ \partial _{t}w+\mathbf {u}\cdot \nabla w = \Delta w -w + n, \\ \partial _{t}\mathbf {u}+ \nabla P = \Delta \mathbf {u}+ n\nabla \psi, \quad \nabla \cdot \mathbf {u}= 0. \end{array}\displaystyle \right. $$ Here, $\chi(n,v,w,x)$ represents the saturated sensitivity. Our result suggests that suitable saturation can prevent the blow-up arising from the classical Keller-Segel type signal production mechanism without any smallness condition on initial mass.

This paper deals with the two-species chemotaxis system with two chemicals \begin{document}$ \begin{eqnarray*} \left\{ \begin{array}{llll} u_t = d_1\Delta u-\nabla\cdot(u\chi_1(v)\nabla v)+\mu_1 u(1-u-a_1w),\quad x'>under homogeneous Neumann boundary conditions in a bounded domain \begin{document}$ \Omega\subset \mathbb{R}^n $\end{document} ( \begin{document}$ n\geq1 $\end{document} ), where the parameters \begin{document}$ d_1,d_2,d_3,d_4>0 $\end{document} , \begin{document}$ \mu_1,\mu_2>0 $\end{document} , \begin{document}$ a_1,a_2>0 $\end{document} and \begin{document}$ \alpha, \beta>0 $\end{document} . The chemotactic function \begin{document}$ \chi_i $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) and the signal production function \begin{document}$ f_i $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are smooth. If \begin{document}$ n = 2 $\end{document} , it is shown that this system possesses a unique global bounded classical solution provided that \begin{document}$ |\chi'_i| $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are bounded. If \begin{document}$ n\leq3 $\end{document} , this system possesses a unique global bounded classical solution provided that \begin{document}$ \mu_i $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are sufficiently large. Specifically, we first obtain an explicit formula \begin{document}$ \mu_{i0}>0 $\end{document} such that this system has no blow-up whenever \begin{document}$ \mu_i>\mu_{i0} $\end{document} . Moreover, by constructing suitable energy functions, it is shown that: \begin{document}$ \bullet $\end{document} If \begin{document}$ a_1,a_2\in(0,1) $\end{document} and \begin{document}$ \mu_1 $\end{document} and \begin{document}$ \mu_2 $\end{document} are sufficiently large, then any global bounded solution exponentially converges to \begin{document}$\bigg(\frac{1-a_1}{1-a_1a_2},f_1(\frac{1-a_2}{1-a_1a_2})/\alpha,\frac{1-a_2}{1-a_1a_2},$\end{document} \begin{document}$ f_2(\frac{1-a_1}{1-a_1a_2})/\beta\bigg)$\end{document} as \begin{document}$ t\rightarrow\infty $\end{document} ; \begin{document}$ \bullet $\end{document} If \begin{document}$ a_1>1>a_2>0 $\end{document} and \begin{document}$ \mu_2 $\end{document} is sufficiently large, then any global bounded solution exponentially converges to \begin{document}$ (0,f_1(1)/\alpha,1,0) $\end{document} as \begin{document}$ t\rightarrow\infty $\end{document} ; \begin{document}$ \bullet $\end{document} If \begin{document}$ a_1 = 1>a_2>0 $\end{document} and \begin{document}$ \mu_2 $\end{document} is sufficiently large, then any global bounded solution algebraically converges to \begin{document}$ (0,f_1(1)/\alpha,1,0) $\end{document} as \begin{document}$ t\rightarrow\infty $\end{document} .

This paper is concerned with the following chemotaxis-growth system u t = Δ u − ∇ ⋅ u ∇ v + μ ( u − u α ) , x ∈ Ω , t > 0 , v t = Δ v − v + w , x ∈ Ω , t > 0 , w t = Δ w − w + u , x ∈ Ω , t > 0 , in a smooth bounded domain Ω ⊂ R n ( n ⩾ 2 ) with nonnegative initial data and null Neumann boundary condition, where μ > 0 , α > 1 . It is stated that if α > n 4 + 1 2 , the solution is globally bounded. Moreover, if μ > 0 is sufficiently large, the solution ( u , v , w ) emanating from nonnegative initial data u 0 , v 0 , w 0 with u 0 ⁄ ≡ 0 is globally bounded and satisfies ‖ u ⋅ , t − 1 ‖ L ∞ Ω + ‖ v ⋅ , t − 1 ‖ L ∞ Ω + ‖ w ⋅ , t − 1 ‖ L ∞ Ω → 0 as t → ∞ .

Researchers have long examined the structure of animal advertisement signals, but comparatively little is known about how often these signals are repeated and what factors predict variation in signaling rate across species. Here, we focus on acoustic advertisement signals to test the hypothesis that calling males experience a tradeoff between investment in the duration or complexity of individual calls and investment in signaling over long time periods. This hypothesis predicts that the number of signals that a male produces per 24 h will negatively correlate with (1) the duration of sound that is produced in each call (the sum of all pulses) and (2) the number of sound pulses per call. To test this hypothesis, we measured call parameters and the number of calls produced per 24 h in 16 species of sympatric phaneropterine katydids from the Panamanian rainforest. This assemblage also provided us with the opportunity to test a second taxonomically specific hypothesis about signaling rates in taxa such as phaneropterine katydids that transition from advertisement calls to mating duets to facilitate mate localization. To establish duets, male phaneropterine katydids call and females produce a short acoustic reply. These duets facilitate searching by males, females, or both sexes, depending on the species. We test the hypothesis that males invest either in calling or in searching for females. This hypothesis predicts a negative relationship between how often males signal over 24 h and how much males move across the landscape relative to females. For the first hypothesis, there was a strong negative relationship between the number of signals and the duration of sound that is produced in each signal, but we find no relationship between the number of signals produced per 24 h and the number of pulses per signal. This result suggests the presence of cross-taxa tradeoffs that limit signal production and duration, but not the structure of individual signals. These tradeoffs could be driven by energetic limitations, predation pressure, signal efficacy, or other signaling costs. For the second hypothesis, we find a negative relationship between the number of signals produced per day and proportion of the light trap catch that is male, likely reflecting males investing either in calling or in searching. These cross-taxa relationships point to the presence of pervasive trade-offs that fundamentally shape the spatial and temporal dynamics of communication.

In this paper we study the quasilinear fully parabolic chemotaxis system with indirect signal production and logistic source: u t = ∇ ⋅ ( D ( u ) ∇ u − S ( u ) ∇ v ) + f ( u ) , v t = Δ v − a 1 v + b 1 w , w t = Δ w − a 2 w + b 2 u , under homogeneous Neumann boundary conditions in a bounded and smooth domain Ω ⊂ R n ( n ≥ 1 ), where a i , b i > 0 ( i = 1 , 2 ), D , S ∈ C 2 ( [ 0 , ∞ ) ) and f : R → R is a smooth function generalizing the logistic source f ( s ) = b − μ s r for all s ≥ 0 with b ≥ 0 , μ > 0 and r ≥ 1 . We obtain the global boundedness of solutions in four cases: (i) the self-diffusion dominates the cross-diffusion; (ii) the logistic source suppresses the cross-diffusion; (iii) the logistic dampening balances the cross-diffusion with μ > 0 suitably large; (iv) the self-diffusion and the logistic source both balance the cross-diffusion to some extent with μ > 0 arbitrary. As corollaries, we also consider the global boundedness of solutions for the quasilinear attraction-repulsion chemotaxis model with logistic source: u ˜ t = ∇ ⋅ ( D ( u ˜ ) ∇ u ˜ ) − χ ∇ ⋅ ( u ˜ ∇ z ) + ξ ∇ ⋅ ( u ˜ ∇ w ˜ ) + f ( u ˜ ) , z t = Δ z − ρ z + η u ˜ , w ˜ t = Δ w ˜ − δ w ˜ + γ u ˜ , where χ , η , ξ , γ , ρ , δ > 0 .

This work is concerned with a quasilinear parabolic–parabolic chemotaxis model with nonlinear signal production: u t = ∇ ⋅ ( ( 1 + u ) − α ∇ u ) − ∇ ⋅ ( u ( 1 + u ) β − 1 ∇ v ) + f ( u ) , v t = Δ v − v + u γ , with nonnegative initial data under homogeneous Neumann boundary conditions in a smooth bounded domain, where α , β ∈ R and γ > 0 . The logistic type source term f ( u ) satisfies that either f ( u ) ≡ 0 or f ( u ) = r u − μ u k with r ∈ R , μ > 0 and k > 1 . The global-in-time existence and uniform-in-time boundedness of solutions are established under specific parameters conditions, which improves the known results.

This paper deals with the following two-species chemotaxis system \begin{document}$\left\{ \begin{array}{*{35}{l}} \ \ {{u}_{t}}=\Delta u-{{\chi }_{1}}\nabla \cdot (u\nabla v)+{{\mu }_{1}}u(1-u-{{a}_{1}}w), & x\in \Omega ,t>0, & \\ \ \ {{v}_{t}}=\Delta v-v+h(w), & x\in \Omega ,t>0, & \\ \ \ {{w}_{t}}=\Delta w-{{\chi }_{2}}\nabla \cdot (w\nabla z)+{{\mu }_{2}}w(1-w-{{a}_{2}}u), & x\in \Omega ,t>0, & \\ \ \ {{z}_{t}}=\Delta z-z+h(u),& x\in \Omega ,t>0, & \\\end{array} \right.$ \end{document} under homogeneous Neumann boundary conditions in a bounded domain \begin{document}$Ω\subset\mathbb{R}^{n}$\end{document} with smooth boundary. The parameters in the system are positive and the signal production function h is a prescribed C1-regular function. The main objectives of this paper are two-fold: One is the existence and boundedness of global solutions, the other is the large time behavior of the global bounded solutions in three competition cases (i.e., a weak competition case, a partially strong competition case and a fully strong competition case). It is shown that the unique positive spatially homogeneous equilibrium \begin{document}$(u_{*}, v_{*}, w_{*}, z_{*})$\end{document} may be globally attractive in the weak competition case (i.e., \begin{document}$0 ), while the constant stationary solution (0, h(1), 1, 0) may be globally attractive and globally stable in the partially strong competition case (i.e., \begin{document}$a_{1}>1>a_{2}>0$\end{document} ). In the fully strong competition case (i.e. \begin{document}$a_{1}, a_{2}>1$\end{document} ), however, we can only obtain the local stability of the two semi-trivial stationary solutions (0, h(1), 1, 0) and (1, 0, 0, h(1)) and the instability of the positive spatially homogeneous \begin{document}$(u_{*}, v_{*}, w_{*}, z_{*})$\end{document} . The matter which species ultimately wins out depends crucially on the starting advantage each species has.

This paper deals with a fully parabolic singular chemotaxis-(growth) system with indirect signal production or consumption $$\begin{aligned} \left\{ \begin{aligned}&u_t=\Delta u-\chi \nabla \cdot \left( \frac{u}{v}\nabla v\right) +f(u),&(x,t)\in \Omega \times (0,\infty ), \\&v_t=\Delta v+h(v,w),&(x,t)\in \Omega \times (0,\infty ), \\&w_t=\Delta w- w+u,&(x,t)\in \Omega \times (0,\infty ), \end{aligned} \right. \end{aligned}$$ under homogeneous Neumann boundary conditions in a smooth convex bounded domain $$\Omega \subset {\mathbb {R}}^{2}$$ , where $$\chi >0$$ . When $$f(u)=0$$ , $$h(v,w)=-v+w$$ , we prove that the solution (u, v, w) of this model is globally uniformly bounded in time and exponentially converges to the steady state $$(\overline{u_{0}},\overline{u_{0}},\overline{u_{0}})$$ in the norm of $$L^{\infty }(\Omega )$$ provided that $$\chi 0$$ , where $$\overline{u_{0}}:=\frac{1}{|\Omega |}\int _{\Omega }u_{0}(x)\mathrm{d}x$$ . Moreover, in the case of $$f(u)=ru-\mu u^{2}$$ , $$h(v,w)=-v+w$$ , where $$r\in {\mathbb {R}}$$ , and $$\mu >0$$ , we obtain the global existence of solutions for this system. Furthermore, under the conditions of $$f(u)=ru-\mu u^{2}$$ , $$h(v,w)=-vw$$ and $$\mu >0$$ , $$r>0$$ , the solution (u, v, w) is also global in time.

Postharvest diseases are the primary reason causing postharvest loss of fruits and vegetables. Although fungicides show an effective way to control postharvest diseases, the use of fungicides is gradually being restricted due to safety, environmental pollution, and resistance development in the pathogen. Induced resistance is a new strategy to control postharvest diseases by eliciting immune activity in fruits and vegetables with exogenous physical, chemical, and biological elicitors. After being stimulated by elicitors, fruits and vegetables respond immediately against pathogens. This process is actually a continuous signal transduction, including the generation, transduction, and interaction of signal molecules. Each step of response can lead to corresponding physiological functions, and ultimately induce disease resistance by upregulating the expression of disease resistance genes and activating a variety of metabolic pathways. Signal molecules not only mediate defense response alone, but also interact with other signal transduction pathways to regulate the disease resistance response. Among various signal molecules, the second messenger (reactive oxygen species, nitric oxide, calcium ions) and plant hormones (salicylic acid, jasmonic acid, ethylene, and abscisic acid) play an important role in induced resistance. This article summarizes and reviews the research progress of induced resistance in recent years, and expounds the role of the above-mentioned signal molecules in induced resistance of harvested fruits and vegetables, and prospects for future research.

In animal communication, receivers benefit from signals providing reliable information on signallers’ traits of interest. Individuals involved in conflicts, such as competition between rivals, should pay particular attention to cues that are ‘unfakeable’ by the senders due to the intrinsic properties of the production process. In bioacoustics, the best-known example of such ‘index signals’ is the relationship between a sender’s body size and the dominant frequency of their vocalizations. Dominant frequency may however not only depend on an animal’s morphology but also on the interaction between the sound production system and its immediate environment. Here, we experimentally altered the environment surrounding calling frogs and assessed its impact on the signal produced. More specifically, we altered water level, which forced frogs to float on the surface and tested how this manipulation affected the shuttling of air between the lungs and the vocal sac, and how this in turn impacted the calls’ dominant frequency. Our results show that frogs that are floating are able to fully inflate their lungs and vocal sacs, and that the associated change in airflow or air pressure is correlated with a decrease of call dominant frequency.

Inconsistent signaling alters the landscape of sexual selection by shielding low-quality males from selection., Like political stump speeches and product advertisements, animal signals are highly repetitive and function to persuade receivers to adopt behaviors benefiting the signaler. And like potential constituents and consumers, receivers assess signals to inform their behavioral decisions. However, inconsistency in sexual signals is widespread and potentially injects uncertainty into mating decisions. Here, we show that females fail to make optimal mating decisions based on assessments of signal quality due to inconsistency in signal production. Natural levels of inconsistency markedly reduced female preference expression for a nonarbitrary signal of male quality. Inconsistency reshaped preferences even more profoundly than the better-known impediment of ambient noise. To our knowledge, this is the first demonstration of how inconsistent messaging degrades optimal decision-making in animals, with implications for understanding signal evolution.

In this paper, we study a chemotaxis system with signal-dependent motility, indirect signal production and generalized logistic source in a smooth bounded domain. By using a priori estimates, some important inequalities and the well-known standard Alikakos–Moser iteration, we establish the global existence of the solution for such kind of chemotaxis system. More precisely, we show that if $$l>\max \left\{ \frac{n}{2},1\right\} $$, $$\lambda \in {\mathbb {R}}$$, $$\mu >0$$ and $$\delta >0$$, then for all sufficiently smooth initial data the system $$\begin{aligned} {\left\{ \begin{array}{ll} u_t=\Delta (\gamma (v)u)+\lambda u-\mu u^l,&{}x\in \Omega ,\,t>0,\\ v_t=\Delta v-v+w,&{}x\in \Omega ,\,t>0,\\ w_t=-\delta w+u,&{}x\in \Omega ,\,t>0, \end{array}\right. } \end{aligned}$$possesses a unique global-in-time solution. Moreover, the solution is shown to approach $$\begin{aligned} \left( \left( \frac{\lambda _+}{\mu }\right) ^{\frac{1}{l-1}},\frac{1}{\delta }\left( \frac{\lambda _+}{\mu }\right) ^{\frac{1}{l-1}},\frac{1}{\delta }\left( \frac{\lambda _+}{\mu }\right) ^{\frac{1}{l-1}}\right) \end{aligned}$$in the large time limit under some extra hypotheses, where $$\lambda _+=\max \{\lambda ,0\}$$.

Multimodal signaling is nearly ubiquitous across animal taxa. While much research has focused on male signal production contributing to female mate-choice or preferences, females often give their own multimodal signals during intersexual communication events. Multimodal signal components are often classified based on whether they contain redundant information (e.g., the backup hypothesis) or non-redundant information (e.g., the multiple messages hypothesis) from the perspective of the receiver. We investigated the role of two different female vocalizations produced by the female house mouse (Mus musculus): the broadband, relatively low-frequency squeaks (broadband vocalizations or BBVs,), and the higher-frequency ultrasonic vocalizations (USVs). These female vocalizations may convey differently valenced information to the male receivers. We paired these vocalizations with and without female urine to examine the influence of combining information across multiple modalities. We found evidence that female urine and vocalizations act as non-redundant multimodal cues as males responded with different behaviors and vocalization rates depending on the female signal presented. Additionally, male mice responded with greater courtship effort to the multimodal combination of female USVs paired with female urine than any other signal combination. These results suggest that the olfactory information contained in female urine provides the context by which males can then evaluate potentially ambiguous female vocalizations.

In this work we consider the chemotaxis system with singular sensitivity and signal production in a two dimensional bounded domain. We present the global existence of weak solutions under appropriate regularity assumptions on the initial data. Our results generalize some well-known results in the literature.

Electrochemical immunosensors are antibody-based affinity biosensors with a high impact on clinical, environmental, food, and pharmaceutical analysis. In general, the analytical performance of these devices is critically determined by the materials and reagents used for their construction, signal production and amplification. Dendrimers are monodisperse and highly branched polymers with three-dimensional structures widely employed as “soft” nanomaterials in electrochemical immunosensor technology. This review provides an overview on the state-of-the-art in dendrimer-based electrochemical immunosensors, focusing on those using polyamidoamine and poly (propylene imine) dendrimers. Special emphasis is given to the most original methods recently reported for the construction of immunosensor architectures incorporating dendrimers, as well as to novel sensing approaches based on dendrimer-assisted signal enhancement strategies.

This paper is concerned with radially symmetric solutions of the Keller–Segel system with nonlinear signal production, as given by in the ball for and R > 0, where f is a suitably regular function generalizing the prototype determined by the choice , , with . The main results assert that if in this setting the number κ satisfies then for any prescribed mass level m > 0, there exist initial data u 0 with , for which the solution of the corresponding Neumann initial-boundary value problem blows up in finite time. The condition in () is essentially optimal and is indicated by a complementary result according to which in the case , for widely arbitrary initial data, a global bounded classical solution can always be found.

This work considers the chemotaxis-growth system u t = Δ u − ∇ ⋅ ( u ∇ v ) + u − u α , v t = Δ v − v + w , w t = u − δ w , in a smoothly bounded domain Ω ⊂ R n , n ≥ 2 , with zero-flux boundary conditions, where δ > 0 and α > 1 are given positive parameters. In the case when n = 3 and α = 2 , the global existence and boundedness of smooth solutions to this system was previously asserted in Hu and Tao (2016). Inspired by an approach newly developed in Tao and Winkler (2015), the present work improves the aforementioned result to a general case when n ≥ 2 and α > n 2 .

These notes aim to provide a deeper insight on the specifics of two articles dealing with chemotaxis models with nonlinear production. More precisely, we are referring to the papers “Boundedness of solutions to a quasilinear parabolic–parabolic chemotaxis model with nonlinear signal production” by Tao et al. (2019) [2] and “Boundedness for a fully parabolic Keller–Segel model with sublinear segregation and superlinear aggregation” by Frassu and Viglialoro (2021) [1] . These works, independently published in these last years, present results leaving open room for further improvement. Indeed, in the first a gap in the proof of the main claim appears, whereas the cornerstone assumption in the second is not sharp. In these pages we give a more complete picture to the relative underlying comprehension.

The purpose of this paper is to study radially symmetric solutions of a parabolic–elliptic chemotaxis system (0.1) u t = Δ u − ∇ ⋅ ( f ( u ) ∇ v ) in B R × ( 0 , + ∞ ) , 0 = Δ v − μ ( t ) + g ( u ) in B R × ( 0 , + ∞ ) subject to homogeneous Neumann boundary conditions, where B R = B R ( 0 ) ⊂ R n with n ⩾ 1 , R > 0 and μ ( t ) = 1 | B R | ∫ B R g ( u ( x , t ) ) d x denotes the time-dependent spatial mean of g ( u ) . The chemosensitivity f and nonlinear signal production g are suitably regular functions. We show that the blow-up phenomenon of radially symmetric solution ( u , v ) of (0.1) in finite time for some initial datum u 0 , when f ( ξ ) ⩾ K ξ k and g ( ξ ) ⩾ L ξ l for all ξ ⩾ 1 with K , k , L , l > 0 and k + l − 1 > 2 n . However, system (0.1) admits a global bounded classical solution for arbitrary initial datum when f ( ξ ) ⩽ K ξ k and g ( ξ ) ⩽ L ξ l for all ξ ⩾ 1 with k + l − 1 2 n .

Acoustic signal production is affected by allometric relationships, by which the larger the animal, the lower its call frequency. In this paper, three evolutionary acoustic hypotheses were tested: the Signal-to-Noise Ratio Hypothesis (SNRH), in which evolution maximizes call ranges by increasing the signal-to-noise ratio; the Stimulus Threshold Hypothesis (STH), in which evolution maximizes the range of a specific signal threshold; and the Body Size Hypothesis (BSH), in which the emission of long wavelengths is enabled by body size. Three spectral metrics were measured, Dominant Frequency (FDOM), Minimum Fundamental Frequencies (FFMIN), and Maximum Fundamental Frequencies (FFMAX) of Neotropical Parrots, New World Doves, Woodcreepers, Tinamous, and Thrushes. A Ranged Major Axis (RMA) regression showed that body mass is significantly correlated with all of the spectral parameters in Parrots, Doves, and Woodcreepers, but only with the fundamental frequencies of Tinamous. The FDOM of Parrots corroborated the SNRH. The FFMIN of Woodcreepers and Tinamous corroborated the SNRH and BSH. The FFMAX of Parrots corroborated the STH and BSH. Those acoustic hypotheses could shed light on the evolutionary processes involved in avian communication, although results indicate that these depend on the taxa and spectral parameters considered.

We study the Neumann initial-boundary problem for the chemotaxis system \begin{align*} \left\{\begin{array}{c@{\,}l@{\quad}l@{\,}c} u_{t}&=��u-\nabla\!\cdot(u\nabla v),\ &x\in��,& t>0,\\ v_{t}&=��v-v+u+f(x,t),\ &x\in��,& t>0,\\ \frac{\partial u}{\partial��}&=\frac{\partial v}{\partial��}=0,\ &x\in\partial��,& t>0,\\ u(x,0)&=u_{0}(x),\ v(x,0)=v_{0}(x),\ &x\in��& \end{array}\right. \end{align*} in a smooth, bounded domain $��\subset\mathbb{R}^n$ with $n\geq2$ and $f\in\text{L}^\infty\left([0,\infty);\text{L}^{\frac{n}{2}+��_0}(��)\right)\cap C^��(��\times(0,\infty))$ with some $��>0$ and $��_0\in\left(0,1\right)$. First we prove local existence of classical solutions for reasonably regular initial values. Afterwards we show that in the case of $n=2$ and $f$ being constant in time, requiring the nonnegative initial data $u_0$ to fulfill the property $\smallint_�� u_0\text{d} x, 23 pages

Communication between plants and their animal partners underlies some of the planet’s most ecologically and economically important mutualisms. Study of communication in this context offers many opportunities to address fundamental questions about the costs and benefits of signal production, signal honesty, and receiver cognition. In this special issue, contributors highlight several key areas of current research, including how multiple receivers affect floral signaling, and how signaling may be related across different phases of reproduction. Visual signals are a particular emphasis, including how learning can mediate pollinator preferences, and the evolution of conspicuousness. In light of these focal areas, we summarize current trends towards the study of greater complexity both in terms of floral phenotypes and signaling/interaction networks.

In this paper we develop a new and convenient technique, with fractional Gagliardo-Nirenberg type inequalities inter alia involved, to treat the quasilinear fully parabolic chemotaxis system with indirect signal production: \begin{document}$ u_t = \nabla\cdot(D(u)\nabla u-S(u)\nabla v) $\end{document} , \begin{document}$ \tau_1v_t = \Delta v-a_1v+b_1w $\end{document} , \begin{document}$ \tau_2w_t = \Delta w-a_2w+b_2u $\end{document} , under homogeneous Neumann boundary conditions in a bounded domain \begin{document}$ \Omega\subset\Bbb{R}^{n} $\end{document} ( \begin{document}$ n\geq 1 $\end{document} ), where \begin{document}$ \tau_i,a_i,b_i>0 $\end{document} ( \begin{document}$ i = 1,2 $\end{document} ) are constants, and the diffusivity \begin{document}$ D $\end{document} and the density-dependent sensitivity \begin{document}$ S $\end{document} satisfy \begin{document}$ D(s)\geq a_0(s+1)^{-\alpha} $\end{document} and \begin{document}$ 0\leq S(s)\leq b_0(s+1)^{\beta} $\end{document} for all \begin{document}$ s\geq 0 $\end{document} with \begin{document}$ a_0,b_0>0 $\end{document} and \begin{document}$ \alpha,\beta\in\Bbb R $\end{document} . It is proved that if \begin{document}$ \alpha+\beta and \begin{document}$ n = 1 $\end{document} , or \begin{document}$ \alpha+\beta with \begin{document}$ n\geq 2 $\end{document} , for any properly regular initial data, this problem has a globally bounded and classical solution. Furthermore, consider the quasilinear attraction-repulsion chemotaxis model: \begin{document}$ u_t = \nabla\cdot(D(u)\nabla u)-\chi\nabla\cdot(u\nabla z)+\xi\nabla\cdot(u\nabla w) $\end{document} , \begin{document}$ z_t = \Delta z-\rho z+\mu u $\end{document} , \begin{document}$ w_t = \Delta w-\delta w+\gamma u $\end{document} , where \begin{document}$ \chi,\mu,\xi,\gamma,\rho,\delta>0 $\end{document} , and the diffusivity \begin{document}$ D $\end{document} fulfills \begin{document}$ D(s)\geq c_0(s+1)^{M-1} $\end{document} for any \begin{document}$ s\geq 0 $\end{document} with \begin{document}$ c_0>0 $\end{document} and \begin{document}$ M\in\Bbb R $\end{document} . As a corollary of the aforementioned assertion, it is shown that when the repulsion cancels the attraction (i.e. \begin{document}$ \chi\mu = \xi\gamma $\end{document} ), the solution is globally bounded if \begin{document}$ M>-1 $\end{document} and \begin{document}$ n = 1 $\end{document} , or \begin{document}$ M>2-4/n $\end{document} with \begin{document}$ n\geq 2 $\end{document} . This seems to be the first result for this quasilinear fully parabolic problem that genuinely concerns the contribution of repulsion.

Sustained perfect synchrony of signal production by animals is unrealistic, but even near-synchronous signalling is extremely rare. Near-synchronous signalling has been documented in some orthopteran insects and fireflies, and one kind of frog. This study provides observations and analyses of sustained bouts of impressive near-synchronous calling by a terrestrial breeding frog from Australia, the hip-pocket frog (Assa darlingtoni). Males called in scattered clusters of several individuals from the rainforest floor of northern New South Wales. In eight of nine pairs of semi-isolated males, there was sustained near-synchronous calling in bouts consisting of 16–20 calls and lasting 5–10 min. There was extensive overlap of the pulsed calls, and calls of a lagging male began overlapping that of a leading male after 2–5 pulses of a leader’s call note. In five pairs, one male’s calls were usually in the leading position; in three pairs, leadership frequently switched between males. In the latter interact...

In this paper, the coupled chemotaxis–fluid system $$\begin{aligned} \left\{ \begin{array}{lll} n_t+u\cdot \nabla n=\Delta n-\nabla \cdot (n\nabla c)+rn-\mu n^2,\ \ \ &{}x\in \Omega ,\ t>0,\\ c_t+u\cdot \nabla c=\Delta c-c+f(n),\ \ &{}x\in \Omega ,\ t>0,\\ u_t=\Delta u+\nabla P+n\nabla \phi ,\ \ &{}x\in \Omega ,\ t>0,\\ \nabla \cdot u=0,\ \ &{}x\in \Omega ,\ t>0\\ \end{array}\right. \end{aligned}$$ is considered associated with no-flux boundary conditions in a smooth bounded domain $$\Omega \subset \mathbb {R}^3$$ , where $$r\ge 0$$ and $$\mu >0$$ are given parameters. $$f\in C^1([0, \infty ))$$ is a given function satisfying $$f(s)\le Ks^{\alpha }$$ with $$K>0, \alpha >0$$ for all $$s>0$$ and $$f(0)\ge 0$$ . It is proved that whenever $$\begin{aligned} \frac{1}{2}0$$ , there exists at least a global classical solution that is uniformly bounded, which exhibits the mild saturation effect of signal production.

This paper is concerned with the zero-flux logistic chemotaxis system with nonlinear signal production: $$u_t=\Delta u-\chi \nabla \cdot (u\nabla v)+f(u)$$ , $$v_t=\Delta v-v+g(u)$$ in a bounded and smooth domain $$\Omega \subset {\mathbb {R}}^n$$ ( $$n\ge 1$$ ), where $$\chi >0$$ is a constant, and $$f,g\in C^1({\mathbb {R}})$$ generalize the prototypes $$f(s)=s-\mu s^{\alpha }$$ and $$g(s)=s(s+1)^{\beta -1}$$ with $$\alpha >1$$ and $$\beta ,\mu >0$$ . The existing studies, for the case that the self-diffusion or the logistic-type source prevails over the cross-diffusion singly, have asserted the global boundedness of solutions under the assumption that $$\beta 0$$ suitably large. In the present paper, we prove that if $$\alpha -1=\beta =\frac{2}{n}$$ , then due to the self-diffusion and the logistic kinetics working together, the solutions are globally bounded regardless of the size of $$\mu >0$$ . Note that $$\alpha -1=\beta =\frac{2}{n}$$ reduces to $$\alpha =2$$ and $$\beta =1$$ if $$n=2$$ . Hence, our result covers that of the two-dimensional classical chemotaxis system with logistic source: $$u_t=\Delta u-\chi \nabla \cdot (u\nabla v)+u-\mu u^2$$ , $$v_t=\Delta v-v+u$$ (Osaki et al. in Nonlinear Anal 51:119–144, 2002).

Individuals produce advertisement signals with intended purposes and targets. However, these signals can be received by “eavesdroppers,” who may extract information from them and alter their behavior according to the extracted information. In anuran systems, males congregate at breeding sites to produce advertisement calls to attract receptive females and fend off rival males. Both sexes directly assess these calls in dyadic encounters and make decisions based on the call’s characteristics, e.g., frequency. What is unknown is whether bystander males eavesdrop on these same calls to inform their future competitive decisions. Here, we examined whether male green tree frogs (Hyla cinerea) eavesdrop on competing males, assess their competitor’s call frequency, and respond accordingly. We exposed males to playbacks of two competing males that varied in call frequency—high, average, low—and quantified latency to call, time spent calling, and number of calling bouts. We found that males had reduced latency to call and called more when eavesdropping low-frequency competition, but not average or high-frequency competition. Focal male size also influenced how they responded, with larger males being more responsive than smaller males. Our results indicate that male green tree frogs are capable of eavesdropping on nearby male calls and produce behavioral responses accordingly. Further, it appears males are able to alternate between assessment strategies dependent upon the frequency of the eavesdropped competition. These findings indicate that males not only directly assess an opponent’s call in dyadic encounters, but also indirectly through eavesdropping. Animals produce signals with intended purposes and targets, but which can be received by nearby eavesdroppers. Eavesdropped signals can elicit complex phenotypic changes in the eavesdropper, and lead to significant fitness consequences for the signal producer and eavesdropper. Thus, examining whether and to what extent individuals eavesdrop is an important step in understanding the evolution of signal production and response. Here, we examined whether male green tree frogs, H. cinerea, eavesdrop on nearby competing males and base their own calling behaviors on eavesdropped male’s calling characteristics. Calling behavior was mediated by focal male body size and eavesdropped male’s call frequency. Larger males reduced response latency and called more to nearby low-frequency males, while smaller males reduced response latency to nearby calls of average frequency. These results indicate that males will extract information from their competitive environment through eavesdropping and produce behavioral responses according to the eavesdropped information.

The well-posedness of a chemotaxis system with indirect signal production in a two-dimensional domain is shown, all solutions being global unlike for the classical Keller-Segel chemotaxis system. Nevertheless, there is a threshold value \begin{document}$ M_c $\end{document} of the mass of the first component which separates two different behaviours: solutions are bounded when the mass is below \begin{document}$ M_c $\end{document} while there are unbounded solutions starting from initial conditions having a mass exceeding \begin{document}$ M_c $\end{document} . This result extends to arbitrary two-dimensional domains a previous result of Tao & Winkler (2017) obtained for radially symmetric solutions to a simplified version of the model in a ball and relies on a different approach involving a Liapunov functional.

We propose and study a class of parabolic-ODE models involving chemotaxis and haptotaxis of a species following signals indirectly produced by another, non-motile one. The setting is motivated by cancer invasion mediated by interactions with the tumor microenvironment, but has much wider applicability, being able to comprise descriptions of biologically quite different problems. As a main mathematical feature consituting a core difference to both classical Keller-Segel chemotaxis systems and Chaplain-Lolas type chemotaxis-haptotaxis systems, the considered model accounts for certain types of indirect signal production mechanisms. The main results assert unique global classical solvability under suitably mild assumptions on the system parameter functions in associated spatially two-dimensional initial-boundary value problems. In particular, this rigorously confirms that at least in two-dimensional settings, the considered indirectness in signal production induces a significant blow-up suppressing tendency also in taxis systems substantially more general than some particular examples for which corresponding effects have recently been observed., Comment: 36pages, 2 figures

Phenotypically plastic signals that can be altered in response to changing environmental conditions provide animals with the ability to dynamically signal their current condition or status. Such flexibility might also provide a means of avoiding potential trade-offs between signal components. Among birds, for example, both the timing of expression and the coloration of nuptial plumage are often thought to be honest signals of condition. However, because plumage is a relatively static signal type, birds that express condition-dependent plumage signals may face a trade-off between timing of signal production and signal quality, in that signals produced relatively early may be of lower quality because of seasonal constraints. A related cost may be increased fading or wear of plumage associated with extended duration of signal expression. Male Red-backed Fairywrens (Malurus melanocephalus) exhibit asynchronous development of nuptial red–black plumage, with some individuals molting into nuptial plumag...

We study nonnnegative radially symmetric solutions of the parabolic-elliptic Keller-Segel whole space system \begin{align*} \left\{\begin{array}{c@{\,}l@{\quad}l@{\,}c} u_{t}&=\Delta u-\nabla\!\cdot(u\nabla v),\ &x\in\mathbb{R}^n,& t>0,\\ 0 &=\Delta v+u+f(x),\ &x\in\mathbb{R}^n,& t>0,\\ u(x,0)&=u_{0}(x),\ &x\in\mathbb{R}^n,& \end{array}\right. \end{align*} with prototypical external signal production \begin{align*} f(x):=\begin{cases} f_0\vert x\vert^{-\alpha},&\text{ if }\vert x\vert \leq R-\rho,\\ 0,&\text{ if } \vert x\vert\geq R+\rho,\\ \end{cases} \end{align*} for $R\in(0,1)$ and $\rho\in\left(0,\frac{R}{2}\right)$, which is still integrable but not of class $\text{L}^{\frac{n}{2}+\delta_0}(\mathbb{R}^n)$ for some $\delta_0\in[0,1)$. For corresponding parabolic-parabolic Neumann-type boundary-value problems in bounded domains $\Omega$, where $f\in\text{L}^{\frac{n}{2}+\delta_0}(\Omega)\cap C^{\alpha}(\Omega)$ for some $\delta_0\in(0,1)$ and $\alpha\in(0,1)$, it is known that the system does not emit blow-up solutions if the quantities $\|u_0\|_{\text{L}^{\frac{n}{2}+\delta_0}(\Omega)}, \|f\|_{\text{L}^{\frac{n}{2}+\delta_0}(\Omega)}$ and $\|v_0\|_{\text{L}^{\theta}(\Omega)}$, for some $\theta>n$, are all bounded by some $\varepsilon>0$ small enough. We will show that whenever $f_0>\frac{2n}{\alpha}(n-2)(n-\alpha)$ and $u_0\equiv c_0>0$ in $\overline{B_1(0)}$, a measure-valued global-in-time weak solution to the system above can be constructed which blows up immediately. Since these conditions are independent of $R\in(0,1)$ and $c_0>0$, we will thus prove the criticality of $\delta_0=0$ for the existence of global bounded solutions under a smallness conditions as described above., Comment: 21 pages

Developing a well-defined nanostructure that can provide strong, reproducible, and stable SERS signals is quite important for the practical application of surface-enhanced Raman scattering (SERS) sensors. We report here a novel single nanowire (NW) on graphene (SNOG) structure as an efficient, reproducible, and stable SERS-active platform. Au NWs having a well-defined single-crystal geometry on a monolayer graphene-coated metal film can form a well-defined, continuous nanogap structure that provides extremely reproducible and stable SERS signals. The in-NW reproducibility was verified by 2-dimensional Raman mapping, and the NW-to-NW reproducibility was verified by the cumulative curves of 32 SERS spectra. The simulation also indicated that a highly regular, line-shaped hot spot formed between the Au NW and graphene. Furthermore, SNOG platforms showed improved photostability and long-term oxidation immunity. We anticipate that SNOG platforms will be appropriate for practical biological and chemical sensor applications that demand reproducible, stable, and strong signal production.

This work considers a chemotaxis system with signal-dependent motility in a smooth bounded domain Ω ⊂ R n . If λ ∈ R , μ > 0 and l > max ⁡ { n + 2 4 , 1 } are constants, then the system { u t = Δ ( γ ( v ) u ) + λ u − μ u l , x ∈ Ω , t > 0 , v t = Δ v − v + w , x ∈ Ω , t > 0 , w t = Δ w − w + u , x ∈ Ω , t > 0 , with homogeneous Neumann boundary conditions possesses a global solution. Moreover, the solution satisfies ‖ u ( ⋅ , t ) − ( λ + μ ) 1 l − 1 ‖ L ∞ + ‖ v ( ⋅ , t ) − ( λ + μ ) 1 l − 1 ‖ L ∞ + ‖ w ( ⋅ , t ) − ( λ + μ ) 1 l − 1 ‖ L ∞ → 0 as t → ∞ under some extra hypotheses, where λ + = max ⁡ { λ , 0 } .

We consider a quasilinear chemotaxis system involving logistic source { u t = ∇ ⋅ ( D ( u ) ∇ u ) − ∇ ⋅ ( S ( u ) ∇ v ) + μ ( u − u γ ) , x ∈ Ω , t > 0 , v t = Δ v − v + w , x ∈ Ω , t > 0 , w t = Δ w − w + u , x ∈ Ω , t > 0 , with nonnegative initial data under homogeneous Neumann boundary conditions in a smooth bounded domain Ω ⊂ R n ( n ⩾ 1 ) . Here, constants μ > 0 , γ > 1 , and D, S are smooth functions fulfilling D ( s ) ⩾ K 0 ( s + 1 ) α , | S ( s ) | ⩽ K 1 s ( s + 1 ) β − 1 for all s ⩾ 0 with α , β ∈ R and K 0 , K 1 > 0 . Then, if β ⩽ γ − 1 , the nonnegative classical solution ( u , v , w ) is global in time and bounded. Moreover, if μ > 0 is sufficiently large, this global bounded solution with nonnegative initial data ( u 0 , v 0 , w 0 ) satisfies ‖ u ( ⋅ , t ) − 1 ‖ L ∞ ( Ω ) + ‖ v ( ⋅ , t ) − 1 ‖ L ∞ ( Ω ) + ‖ w ( ⋅ , t ) − 1 ‖ L ∞ ( Ω ) → 0 as t → ∞ .

A fully parabolic chemotaxis system with singular sensitivity and nonlinear signal production is considered. Under suitable assumption on the sensitivity value and the signal production term, it is shown that this system admits a global classical solution. The proof is based on a series of a priori estimate techniques.

In this paper, a quasilinear chemotaxis system of parabolic-elliptic type (0.1) { u t = ∇ ⋅ ( φ ( u ) ∇ u ) − ∇ ⋅ ( u ∇ v ) x ∈ Ω , t > 0 , 0 = Δ v − μ ( t ) + f ( u ) , μ ( t ) : = 1 | Ω | ∫ Ω f ( u ( ⋅ , t ) ) , x ∈ Ω , t > 0 is considered associated with homogeneous Neumann boundary conditions in a smooth bounded domain Ω ⊂ R n , n ≥ 1 . The diffusivity φ ( ξ ) ∈ C 2 ( [ 0 , ∞ ) ) is a positive function and we particularly suppose that φ ( ξ ) = C 0 ( 1 + ξ ) − m for all ξ ≥ 0 with C 0 > 0 and m ∈ R . f is a suitably regular positive function given by f ( ξ ) = K ( 1 + ξ ) κ for all ξ ≥ 0 with parameters K > 0 and κ > 0 . It is shown that there exist regular initial data u 0 such that • if κ + m 2 n , then all solutions of (0.1) are global and bounded; • if κ + m > 2 n , however, there exists nonnegative radially symmetric initial data u 0 such that the corresponding solution of (0.1) blows up in finite time. The critical exponent 2 n seems to be essentially optimal which was given by [30] .

Honesty is crucial in animal communication when signallers are conveying information about their condition. Condition dependence implies a cost to signal production; yet, evidence of such cost is scarce. We examined the effects of naturally occurring injury on the quality and salience of olfactory signals in ring-tailed lemurs (Lemur catta). Over a decade, we collected genital secretions from 23 (13 male, 10 female) adults across 34 unique injuries, owing primarily to intra-group fights. Using gas chromatography-mass spectrometry, we tested for differences in the chemical composition of secretions across pre-injury, injury and recovery, in animals that did and did not receive antibiotics. Lemur genital secretions were significantly dampened and altered during injury, with patterns of change varying by sex, season and antibiotics. Using behavioural bioassays (excluding odorants from antibiotic-treated animals), we showed that male ‘recipients’ discriminated injury status based on scent alone, directing more competitive counter marking towards odorants from injured vs. uninjured male ‘signallers.’ That injured animals could not maintain their normal signatures provides rare evidence of the energetic cost to signal production. That conspecifics detected olfactory-encoded ‘weakness’ suggests added behavioural costs: By influencing the likelihood of intra- or inter-sexual conflict, condition-dependent signals could have important implications for socio-reproductive behaviour.

The emergence and maintenance of animal communication systems requires the co-evolution of signal and receiver. Frogs and toads rely heavily on acoustic communication for coordinating reproduction and typically have ears tuned to the dominant frequency of their vocalizations, allowing discrimination from background noise and heterospecific calls. However, we present here evidence that two anurans, Brachycephalus ephippium and B. pitanga, are insensitive to the sound of their own calls. Both species produce advertisement calls outside their hearing sensitivity range and their inner ears are partly undeveloped, which accounts for their lack of high-frequency sensitivity. If unheard by the intended receivers, calls are not beneficial to the emitter and should be selected against because of the costs associated with signal production. We suggest that protection against predators conferred by their high toxicity might help to explain why calling has not yet disappeared, and that visual communication may have replaced auditory in these colourful, diurnal frogs.

International audience; Under natural conditions bottlenose dolphins (Tursiops truncatus) spend their time mostly feeding and then travelling, socializing, or resting. These activities are not randomly distributed, with feeding being higher in early morning and late afternoon. Social activities and vocal behavior seem to be very important in dolphin daily activity. This study aimed to describe the activity time-budget and its relation to vocal behavior for dolphins in a zoological park. We recorded behaviors and vocalizations of six dolphins over 2 months. All subjects performed more non-agonistic social interactions and play in the morning than in the afternoon. The different categories of vocalizations were distributed non-randomly throughout the day, with more chirps in the afternoon, when the animals were “less social.” The most striking result was the strong correlation between activities and the categories of vocalizations produced. The results confirm the association between burst pulses and whistles with social activities, but also reveal that both are also associated with solitary play. More chirps were produced when dolphins were engaged in socio-sexual behaviors, emphasizing the need for further questioning about the function of this vocal category. This study reveals that: (i) in a group kept in zoological management, social activities are mostly present in the morning; and (ii) the acoustic signals produced by dolphins may give a reliable representation of their current activities. While more studies on the context of signal production are needed, our findings provide a useful tool for understanding free ranging dolphin behavior when they are not visible.

This paper studies the two-species chemotaxis system with two indirect signal production and logistic source $$\begin{aligned} \left\{ \begin{array}{l@{\quad }l@{\quad }l@{\quad }l} u_t=\Delta u-\chi _{1}\nabla \cdot (u\nabla v)+\mu _{1}u(1-u),\quad &{}x\in \Omega ,\quad t>0,\\ v_{t} =\Delta v-v+w,\quad &{}x\in \Omega ,\quad t>0,\\ w_{t} =\Delta w-\chi _{2}\nabla \cdot (w\nabla z)+\mu _{2}w(1-w),\quad &{}x\in \Omega ,\quad t>0,\\ z_{t}=\Delta z-z+u,\quad &{}x\in \Omega ,\quad t>0 \end{array} \right. \end{aligned}$$ in a bounded smooth domain \(\Omega \subset \mathbb {R}^3\) with zero-flux boundary conditions, where the parameters \(\chi _{i}\) and \(\mu _{i}\)\((i=1,2)\) are positive. It is shown that this system possesses a unique global-bounded classical solution under the conditions \(\mu _{1}\ge \max \Big \{7\chi _{1}^{2}+1,\frac{51}{2}\Big \}\) and \(\mu _{2}\ge \max \Big \{7\chi _{2}^{2}+1,\frac{51}{2}\Big \}\). Furthermore, whenever \(u_{0}\not \equiv 0\), the solution of the system exponentially stabilizes to the constant stationary solution \(\big (1,1,1,1\big )\) in the norm of \(L^{\infty }(\Omega )\) as \(t\rightarrow \infty \) under the additional conditions \(\mu _{1}>\frac{\chi _{2}^{2}}{8}\) and \(\mu _{2}>\frac{\chi _{1}^{2}}{8}\).

Animals communicate using a vast array of different signals in different modalities. For chimpanzees, vocalizations, gestures and facial expressions are all important forms of communication, yet these signals have rarely been studied together holistically. The current study aimed to provide the first comprehensive repertoire of flexibly combined (‘free’) multimodal (MM) signals, and assess individual and contextual factors influencing production of, and responses to, unimodal (UM) and MM signals in wild chimpanzees. In total, 48 different free MM signals were produced. MM signals were produced at a significantly lower rate than UM signals, but 22 of 26 focal animals were observed to produce free MM signals. The relative production rates of different types of UM and MM signals differed significantly between the behavioural contexts investigated, showing flexible use of signals across contexts. In contrast, individual factors such as age, sex or rank of signaller did not appear to influence the type of signal produced or the likelihood of eliciting a response. Finally, we compared recipient responses to free MM grunt-gesture signals and matched UM component signals and found that these MM signals were more likely to elicit a response than a grunt alone, but were as likely to elicit a response as the gesture alone. The overall findings point to a widespread capacity for wild chimpanzees to flexibly combine signals from different modalities and highlight the importance of adopting a multimodal approach to studying communication.

In animals, signaling behavior is often context-dependent, with variation in the probability of emitting certain signals dependent on fitness advantages. Senders may adjust signaling rate depending on receiver identity, presence of audiences, or noise masking the signal, all of which can affect the benefits and costs of signal production. In the cooperative breeding meerkat Suricata suricatta, group members emit soft contact calls, termed as “close calls”, while foraging in order to maintain group cohesion. Here, we investigated how the close calling rate during foraging was affected by the presence of pups, that produce continuous, noisy begging calls as they follow older group members. Adults decreased their overall close call rate substantially when pups were foraging with the group in comparison to periods when no pups were present. We suggest this decrease was likely due to a masking effect of the loud begging calls, which makes the close call function of maintaining group cohesion partly redundant as the centrally located begging calls can be used instead to maintain cohesion. There was some support that adults use close calls strategically to attract specific pups based on fitness advantages, that is, as the philopatric sex, females should call more than males and more to female pups than male pups. Dominant females called more than dominant males when a pup was in close proximity, while subordinates showed no sex-based differences. The sex of the nearest pup did not affect the calling rate of adults. The study shows that meerkats modify their close call production depending on benefits gained from calling and provides an example of the flexible use of one calling system in the presence of another, here contact calls versus begging calls, within the same species.

Many sexually selected traits are static throughout the breeding season. Some vary within the breeding season, however, typically in response to physiological changes. Most work attempting to understand the mechanisms underlying phenotypic changes has occurred in the laboratory, with comparatively less research examining how changes to physiology affect signal production in natural populations. Here, we report intraseasonal plasticity in abdominal and throat patch color of Prairie Lizards (Sceloporus consobrinus), and examine how changes in body size, body condition, and testosterone underlie intraseasonal variation. We found that changes in testosterone best explain why throat patches of Prairie Lizards become less blue throughout the breeding season. If females reproduce with males based on patch color, then individual changes in patch phenotypes could have important consequences if signaling morphology is asynchronous among males.

The evolution of biosonar (production of high-frequency sound and reception of its echo) was a key innovation of toothed whales and dolphins (Odontoceti) that facilitated phylogenetic diversification and rise to ecological predominance. Yet exactly when high-frequency hearing first evolved in odontocete history remains a fundamental question in cetacean biology. Here, we show that archaic odontocetes had a cochlea specialized for sensing high-frequency sound, as exemplified by an Oligocene xenorophid, one of the earliest diverging stem groups. This specialization is not as extreme as that seen in the crown clade. Paired with anatomical correlates for high-frequency signal production in Xenorophidae, this is strong evidence that the most archaic toothed whales possessed a functional biosonar system, and that this signature adaptation of odontocetes was acquired at or soon after their origin.