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Here we describe an unusual fossil assemblage found inside a crotovine from the late Pliocene Chapadmalal ‘Formation’ (Buenos Aires Province). This assemblage contains the greatest vertebrate diversity recovered inside an ichnofossil of this type, including skeletal remains of dasypodids, didelphids, procyonids, anurans and caviomorph rodents within coprolites and disaggregated scatological waste. We describe four general size types for crotovines and palaeoburrows found in the Pliocene to Holocene of Argentina and Brazil, of which the structure found corresponds to the ‘mid-large’ size type and is linked to the activity of the large dasypodidRingueletia simpsoni. The scatological remains are assigned to a small-sized carnivorous mammal with a body mass of between 1 and 6 kg. Within the guild of Chapadmalalan omnivorous–carnivorous mammals, this inferred mass range is restricted to large didelphids and mid-sized procyonids (represented in the assemblage byThylophorops chapadmalensisandCyonasua lutaria, respectively). The data gathered here confirms that the reoccupation of burrows is a common behaviour in small-sized carnivorous mammals at least since the early Pliocene. In addition, we suggest a predator–prey relationship between the studied carnivores and the most abundant small fossorial mammals of the Pampean Pliocene. [ABSTRACT FROM PUBLISHER]

This paper focuses on the development of behaviours that are critical for the survival of newborn and juvenile mammals of veterinary and wider biological interest. It provides an updated, integrated and comparative analysis of how postnatal maturation of sensory, motor and perceptual capacities support and constrain behavioural interactions between mammalian young and the mother, any littermates and the environment. Young that are neurologically exceptionally immature, moderately immature and mature at birth are compared, and include, for example, marsupial joeys, rodent pups and ruminant offspring. Mothers in these three groups exhibit distinctive patterns of birthing and postnatal care behaviours. To secure survival of the young, maternal care must compensate for behavioural inadequacies imposed by the limited sensory capacities the young possess at each stage. These sensory capacities develop in a predictable sequence in most mammals such that before birth the sequence progresses to an extent that parallels the degree of neurological maturity reached at birth. The extent of neurological maturity is likewise reflected in how long it takes after birth for the necessary brain circuit connectivity to develop sufficiently to support cortically based cognitive modulation of behaviour. This takes several months, days-to-weeks or minutes-to-hours in young that are, respectively, neurologically exceptionally immature, moderately immature, or mature at birth. Once achieved, cognitive awareness confers a high degree of behavioural flexibility that allows the young to respond more effectively to the unpredictability of their postnatal environments. It is shown that the onset of this cognitively based flexibility in the young of each group coincides with their first exposure to a variable environment that requires such behavioural flexibility. [ABSTRACT FROM PUBLISHER]

1. Serotonin (5-HT) is a primary regulating neurotransmitter involved in aggressive and impulsive behaviours in mammals. Previous studies have also demonstrated that the function of the serotonergic system in regulating aggression is affected by both genetic and environmental factors. The serotonergic system may display similar functions in chickens. 2. Our objective was to investigate the aggressive and impulsive behavioural response to antagonism of the 5-HT1A and 1B receptors in cocks bred for susceptibility and resistance to Marek’s disease (i.e. strain 72and 63, respectively). 3. Cocks from strain 72exhibited increased aggressive behaviours and lower brain 5-HT concentrations compared to strain 63cocks. 4. Antagonism of 5-HT1A receptors increased aggressiveness and reduced serotonin turnover in strain 72, but not strain 63cocks. 5-HT1B receptor antagonism had no effect on aggression or serotonin turnover in either strain. 5. Levels of the serotonin metabolite 5-HIAA, but not absolute central 5-HT levels, were altered in both strains following 5-HT1B antagonism, but only in strain 72cocks following 5-HT1A antagonism. 6. The data suggest that 5-HT1A and 1B regulate aggression differently in high and low aggressive strains. [ABSTRACT FROM PUBLISHER]

The western giant eland (Tragelaphus derbianus derbianus) needs appropriate management for its survival. We measured the effects of supplemental food on activity and browsing patterns during seasons of scarce natural food resources in 2008 and 2009 for a herd of six animals in the Fathala Reserve (Senegal). In response to the provision of high-quality pods of Acacia albida, animals reduced foraging time in 2008 and allocated it to resting. This pattern corresponds to the animals' behaviour in captivity without foraging versus vigilance trade-offs and with predictable (in time and space) access to food. In 2009, supplemental feeding had no effect on behaviour and was associated with increased foraging and ruminating times than in 2008, suggesting more limited natural food resources in 2009.We recorded high species diversity in the animals' natural diet. Supplemental food did not induce changes in browsing pattern at the plant species level, probably due to small individual effect on total nutrient and energy intake. Food supplementation, however, facilitates the animals overcoming unfavourable conditions or alleviates stress with additional rest, and could therefore assist as a conservation intervention to enhance fitness. [ABSTRACT FROM AUTHOR]

Huddling is a behavioural energy conservation mechanism that is widely used by many small endotherms at low ambient temperatures. Huddling has many benefits, including decreasing the metabolic cost of maintaining body temperature (Tb), reducing the amount of heat lost to the environment, and increasing the local temperature of the nest. To test the effects of huddling on Tb, 10 rock hyrax, Procavia capensis, were housed in outside cages in four groups, varying from one to four individuals. iButtons® were surgically implanted into each rock hyrax to record their Tb every 15 min from August to November. Despite considerable variations in ambient temperatures, the rock hyrax were found to display some degree of heterothermy by varying their mean Tb from 36.70 to 37.72°C (n = 10) but not allowing it to drop below 33.60°C or rise above 39.67°C. Contrary to what was predicted, rock hyrax did not display any significant effects of huddling on Tb, irrespective of group size. [ABSTRACT FROM AUTHOR]

A key benefit and evolutionary driver of group living is reduced predation risk. In white rhinos, groups comprise adult females, their calves and one to six unrelated subadults. Subadults benefit from group living through exposure to novel areas, and protection from territorial males (i.e. 'buddy system'). In contrast, it is unclear whether mothers benefit from group living. To determine if they benefit, or if there is simply no cost, we recorded the vigilance of white rhino mothers in different-sized groups. We predicted that as group size increased, calves would have lower predation risk and mothers would reduce their vigilance. In contrast, we found that vigilance did not decrease as group size increased. Our findings thus indicate that decreased vigilance is not a benefit that white rhino mothers gain from living in groups. Also, costs of group formation are minimal for mothers as their large body size and ability to feed on a wide range of grasses reduces competition with other group members. As a result, we suggest that the benefits obtained by subadults, coupled with the lack of costs to adult females, are the main drivers of group formation in white rhinos. [ABSTRACT FROM AUTHOR]

Wastewater treatment works (WWTWs) are known to provide profitable foraging areas for insectivorous bats in Europe and the New World because of their association with high abundance of pollution-tolerant midges (Diptera). However, bats that feed on these insects may also accumulate metal pollutants such as cadmium and copper in their tissues, with acute or chronic effects on their health. Using a time expansion bat detector, the activity (number of passes and feeding buzzes) of Neoromicia nana (family Vespertilionidae) was quantified at three WWTW points - upstream, the point of wastewater effluent discharge, and downstream - along three urban rivers in South Africa. In addition, metal concentrations in the kidney, liver and muscle tissue of N. nana caught at the sites were quantified. The diversity of aerial insects, sampled over the same period as the bat surveys, was measured using a black light trap and sweep-netting. Relative abundance and feeding activity of N. nana were higher at wastewater-polluted sites than at upstream sites. The most abundant insect order at wastewater-polluted sites and in the diet of resident bats was Diptera. Essential metals (copper, zinc and iron) were detected in all N. nana tissue samples, but the toxic metals cadmium, chromium and nickel were mostly present in tissue of bats at wastewater-polluted sites. Thus, although WWTWs provide an optimal food resource to bats in the short-term, it may pose serious long-term health risks for these top predators. [ABSTRACT FROM AUTHOR]

Many behavioral and physiological processes display diurnal (24-h) rhythms controlled by an internal timekeeping system-the circadian clock. In mammals, a circadian pacemaker is located in the suprachiasmatic nucleus (SCN) of the hypothalamus and synchronizes peripheral oscillators found in most other tissues with the external light-dark (LD) cycle. At the molecular level, circadian clocks are regulated by transcriptional translational feedback loops (TTLs) involving a set of clock genes. The mammalian core TTL includes the transcriptional modulators PER (1-3) and CRY (1//2) that inhibit their own expression by interaction with CLOCK//NPAS2 and BMAL1 (ARNTL). The basic helix-loop-helix transcription factors DEC1 (BHLHE40) and DEC2 (BHLHE41) can interact with this core TTL, forming an accessory feedback mechanism. The authors measured circadian locomotor behavior and clock gene expression in the SCN of Per2//Dec double- and triple-mutant mice to analyze the functional interaction of PER2 and DEC feedback on circadian pacemaker function in the SCN. The data suggest a synergistic interaction of Per2 and Dec1//2 in activity entrainment to a standard LD cycle, correlating with a cumulative deficiency in negative-masking capacities in Per2//Dec double- and triple-mutant mice and suggesting an involvement of Per2-Dec1//2 interactivity in activity-onset regulation and masking under LD, but not under constant conditions. In contrast, under constant darkness (DD) conditions, a deletion of either Dec1 or Dec2 partially rescued the Per2 mutant short-period//arrhythmicity phenotype, accompanied by a restoration of time-of-day effects on clock gene expression in the SCN. Together, these results show an interaction of Per2 and Dec1//2 feedback processes in the SCN with differential modes of interactivity under entrained and free-run conditions. (Author correspondence: ) [ABSTRACT FROM AUTHOR]

Here we describe the stomach contents of nine small mammal species (seven rodents and two didelphid marsupials) co-occurring in an old-growth Atlantic forest area. For four terrestrial rodents, we also compared the importance of arthropods in the diet and the selection of arthropod groups by comparing consumption with availability. Small mammals and arthropods were sampled in a 36-ha grid containing 25 sampling stations spaced every 150 m, and 47 stomach contents were analysed. While plant matter was the predominant item in the stomach contents of two rodents (Oligoryzomys nigripes and Rhipidomys mastacalis), four species presented arthropods as the main food item (the rodents Brucepattersonius soricinus and Oxymycterus dasytrichus, and the marsupials Monodelphis n. sp. and Marmosops incanus) and three consumed more plant matter than arthropods, but had significant amounts of both items (the rodents Delomys sublineatus, Euryoryzomys russatus and Thaptomys nigrita). Our results suggest that differences in diet, coupled with differences in habit and microhabitat preferences, are important factors allowing resource partition among species of the diverse group of co-occurring terrestrial small mammals in Atlantic forest areas. Moreover, arthropods were not preyed opportunistically by any of the four terrestrial rodents, since consumption was not proportional to availability. Rather, selection or rejection of arthropod groups seems to be determined by aspects other than availability, such as nutritional value, easiness of capture and handling or palatability. [ABSTRACT FROM AUTHOR]

This contribution presents a morphofunctional analysis of the previously unknown appendicular skeleton of the paucituberculatans Palaeothentes minutus and Palaeothentes lemoinei from the Santa Cruz Formation (late early Miocene, Santa Cruz province, Argentina), performed in order to infer their locomotor behavior. In addition, a cladistic analysis was conducted to explore the phylogenetic information of postcranial features of Palaeothentes in the context of Marsupialia. The results indicate that Palaeothentes would have been an agile cursorial dweller, with leaping ability, similar to the extant paucituberculatan Caenolestes fuliginosus and the didelphid Metachirus nudicaudatus. This mode of locomotion is evidenced mainly by the following features: proximal location of the deltopectoral crest and bicipital tuberosity, reflecting rapid flexion at the gleno-humeral and elbow joints, respectively; shape of the humero-ulnar and humero-radial joints (deep and high humeral trochlea, deep olecranon fossa, deep trochlear notch, mediolaterally broad proximal trochlear crest), denoting a marked stability for flexion and extension; restrictive acetabulum, showing emphasized congruence at the hip joint; lengthened ischium and prominent femoral tubercle and ischial tuberosity, indicating an increased mechanical advantage of the rectus femoris and hamstring muscles; proximally projected greater trochanter, demonstrating a relatively great mechanical advantage of the gluteal muscles; and configuration of the upper ankle, lower ankle, and transverse tarsal joints, indicative of restrictive rotational movements (right angle between the medial and lateral astragalotibial facets, distal and proximal calcaneo-cuboid facet halves forming a right angle). A cladistic analysis positions Palaeothentes as the sister taxon to the extant Caenolestes, demonstrating that postcranial features support the monophyly of Paucituberculata. [ABSTRACT FROM AUTHOR]

Although the effects of estrogen on sexual behavior in mammals are well known, its role on other types of behavior, including cognition, have only recently been recognized. This review summarizes work conducted in our laboratory and others with the aim of identifying the effects of estrogen on cognitive functions. The first section will briefly describe the neurobiology of estrogen. The second section will discuss the effects of estrogen on cognitive behaviors in mammals, as well as the physiological relevance of these effects and their applicability to human health and disease. The third section will detail the role of estrogen on working memory in humans and nonhuman primates, and in rodents. Finally, the concluding section will briefly describe the relationship between estrogen and the aging brain. INSET: Key issues. [ABSTRACT FROM AUTHOR]

With the ever-growing number of xenobiotics that can potentially contaminate the environment, the determination of their mammalian toxicity is of prime importance. In this context, LD50 tests on rats and mice have been used for a long time to express the relative hazard associated with the acute toxicity of inorganic and organic chemicals. However, these laboratory tests encounter important hurdles. They are costly, time consuming and actively opposed by animal rights activists. Moreover, new legislation policies, such as REACH (Registration, Evaluation, Authorization and Restriction of Chemicals), aim at reducing the use of toxicity tests on vertebrates. Consequently, there is a need to find alternative methods for estimating the acute mammalian toxicity of chemicals. The quantitative structure-activity relationships (QSARs) and interspecies correlations appear particularly suited to reaching this goal. In this context, this paper reviews more than 150 models aiming at predicting rat and mouse LD50 values from molecular descriptors or (and) ecotoxicity data. The interest of these computational tools is discussed. [ABSTRACT FROM AUTHOR]

One way to avoid potential predators is to be sensitive to odour cues, particularly those in faeces and urine, left by predators. This sensitivity has been demonstrated in many solitary, nocturnal, small mammals which may fall victim to ambush predators. We tested the response of Cape ground squirrels, a diurnal, group-living small mammal, to the presence of predator (black-backed jackal) faeces and non-predator (black wildebeest) dung in halted traps, and also predator faeces and non-predator dung outside their burrows. The squirrels showed a significantly higher avoidance of traps scented with predator faeces than both control and non-predator dung-scented traps. They also took significantly longer to emerge from burrows that had predator faeces outside compared with control burrows and burrows with non-predator dung outside and showed a trend for higher vigilance once they emerged from burrows with predator faeces outside. We argue that as diurnal group-living reduces a reliance on olfactory cues, this species is more likely to rely on visual cues and the vigilance of other individuals than nocturnal solitary species that have been the focus of most studies up till now. As a result, squirrels very quickly return to normal behaviour after exposure to a predator cue. Level of sociality is likely to influence responses to olfactory cues of predators and should be the focus of further studies. [ABSTRACT FROM AUTHOR]

Evaluates the report Marine Mammal Populations and Ocean Noise: Determining When Noise Causes Biologically Significant Effects, released by the Committee on Characterizing Biologically Significant Marine Mammal Behavior in 2005. Placement by the committee of the origins of its work in the U.S. National Research Council report; Link between exposure to sound and adverse effects on a marine mammal population; Information on the U.S. Endangered Species Act.

Circadian photoentrainment is the process by which the brain's internal clock becomes synchronized with the daily external cycle of light and dark. In mammals, this process is mediated exclusively by a novel class of retinal ganglion cells that send axonal projections to the suprachiasmatic nuclei (SCN), the region of the brain that houses the circadian pacemaker. In contrast to their counterparts that mediate image-forming vision, SCN-projecting RGCs are intrinsically sensitive to light, independent of synaptic input from rod and cone photoreceptors. The recent discovery of these photosensitive RGCs has challenged the long-standing dogma of retinal physiology that rod and cone photoreceptors are the only retinal cells that respond directly to light and has explained the perplexing finding that mice lacking rod and cone photoreceptors can still reliably entrain their circadian rhythms to light. These SCN-projecting RGCs selectively express melanopsin, a novel opsin-like protein that has been proposed as a likely candidate for the photopigment in these cells. Research in the past three years has revealed that disruption of the melanopsin gene impairs circadian photoentrainment, as well as other nonvisual responses to light such as the pupillary light reflex. Until recently, however, there was no direct demonstration that melanopsin formed a functional photopigment capable of catalyzing G-protein activation in a light-dependent manner. Our laboratory has recently succeeded in expressing melanopsin in a heterologous tissue culture system and reconstituting a pigment with the 11-cis-retinal chromophore. In a reconstituted biochemical system, the reconstituted melanopsin was capable of activating transducin, the G-protein of rod photoreceptors, in a light-dependent manner. The absorbance spectrum of this heterologously expressed melanopsin, however, does not match that predicted by previous behavioral and electophysiological studies. Although melanopsin is clearly the leading candidate for the elusive photopigment of the circadian system, further research is needed to resolve the mystery posed by its absorbance spectrum and to fully elucidate its role in circadian photoentrainment. [ABSTRACT FROM AUTHOR]

The article discusses the social complexity of primate societies. It has been known that primates other than humans have rich social life. The new sociology of simians depicts actors who cannot attain their goals without negotiating with others. Primatologists described the interaction as an indication of the complex sociality in the state of nature. In the sociological literature, social interaction presupposes the presence of several constitutive elements. One difference between simian and human interactions is that for the latter, simultaneity in space and time is difficult to obtain.