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Conditioned place preference (CPP) with both visual and tactile cues, hyperactivity, and stereotypies produced by d-amphetamine (1-10 mg/kg ip, single dose) were studied in CD-1 mice at 2, 3, and 4 weeks from birth. CPP was shown from the youngest age onward in female mice and from 3 weeks in male mice. Hyperactivity was much more pronounced in postweanlings (3 and 4 weeks) than in preweanlings. Stereotypies (at 3.3 and 10 mg/kg) occurred from the youngest age and tended to peak at 3 weeks. Stereotypies may indicate a sickness experience or 'poor welfare' (G. J. Mason, 1991; A. Wall, R. E. Hinson, E. Schmidt, C. Johnston, & A. Streather, 1990) due to an aversive component of amphetamine's action. Therefore, the delayed development of fully fledged amphetamine CPP, relative to cocaine CPP (G. Laviola, G. Dell'Omo, E. Alleva, & G. Bignami, 1992), may be due to an age-dependent diminution of the positive hedonic value of the former drug by negative effects that are minimal or absent in the case of the latter drug.

The European honey buzzard Pernis apivorusis a summer visitor in Europe, wintering mostly in West-central Africa. Previous studies concerning timing of autumn migration in relation to sex groups provided contrasting results. In particular, a field survey made in southern Sweden did not report differences in timing, while a satellite study via GPS tracking on six adults, three males, and three females, revealed that the latter departed earlier. The aim of this 4-year study is to further investigate the timing of autumn migration in this species carrying out observations at the Strait of Messina, a bottleneck located along the Central Mediterranean flyway, between August 10th and September 30th 2016–2019. Adult European honey buzzards concentrated the passage between late August early September, with females passing on average 5 days earlier than males. It is suggested that a different role of sexes concerning exhibition of territorial displays during the late breeding season, would explain differences between sex groups in timing of both moult and autumn migration.

Abstract: Selective predation can be an important force driving the evolution of organisms. In particular, sex-biased predation is expected to have implications for sexual selection, sex allocation and population dynamics. In this study, we analysed sex differences in the predation of the western green lizard (Lacerta bilineata) by the Eurasian kestrel (Falco tinnunculus) during the reproductive season. In addition, we investigated whether the rate of predation differed during the 8-year study period and among the three habitats studied. We collected lizard remains from nest boxes of kestrels. Freshly killed lizards were sexed by visual inspection, whilst the sex of head remains was assigned by analysing the cephalic scale morphology using geometric morphometrics. Our results show that the risk of being predated by a kestrel in our population was overall about 3.55 times higher for males than for females. To our knowledge this is the first study showing a male-biased predation in a lizard species. The selective predation of males was consistent between years over the 8-year study period (1999–2006) and also consistent between the three types of kestrel hunting habitat. Overall predation rates on lizards differed between habitats, depending on the year. We propose that the observed sex-biased predation is mainly due to sex differences in lizard behaviour.

P revious behavioral studies (Minichiello et al., Neuron 1999;24:401–414) showed that mice deficient for the TrkB receptor in the forebrain were unable to learn a swimming navigation task with an invisible platform and were severely impaired in finding a visible platform in the same setup. Likewise, additional behavioral deficits suggested a malfunction of the hippocampus and proximally connected forebrain structures. In order to discriminate whether the behavioral impairment was caused either by deficits in spatial memory and learning, or alternatively by loss of behavioral flexibility, 8 trkBmutant, 13 wild‐type, and 22 heterozygous mice were implanted with transponders and released for 21 days into a large outdoor pen (10 × 10 m). The enclosure contained 2 shelters and 8 computer‐controlled feeder boxes, delivering food portions for every mouse only during their first visit. Every third day, mice received food ad libitum inside the shelters. All mice learned to patrol the boxes correctly within a few days. However, significant differences emerged during those days with free food available. Wild‐type mice remained inside the shelters, while all homozygous mutants continued to patrol the boxes in their habitual way, the heterozygous mutants showing intermediate scores. These and previous data suggest that one of the natural functions of the mouse hippocampus is to comediate behavioral flexibility, and that TrkB receptors might play an essential role in maintaining the neuronal short‐term plasticity necessary for this capacity. Hippocampus 2002;12:27–38. © 2002 Wiley‐Liss, Inc.

We showed previously for mice that size differences of the infrapyramidal hippocampal mossy fiber projection (IIP-MF) correlate with spatial learning abilities. In order to clarify the role of the IIP-MF in a natural environment, we studied the bank vole (Clethrionomys glareolus), adapted to a wide range of different habitats, and the root vole (Microtus oeconomus), living in homogenous grassland habitats with small home ranges. Morphometry on Timm-stained horizontal brain sections of six C. glareolus and six M. oeconomus revealed that the size of the entire mossy fiber projection was 42% larger in C. glareolus than M. oeconomus. C. glareolus had also an IIP-MF projection about 230% larger than that of the root vole. A sample of captured animals was then transferred to the laboratory (C. glareolus, n = 23; M. oeconomus, n = 15) and underwent testing for swimming navigation according to a standardized protocol used to assess water maze learning in about 2,000 normal and transgenic mice. Both species learned faster than laboratory mice. Overall escape times showed no differences, but path length was significantly reduced in C. glareolus, which also showed superior performance in a variety of scores assessing spatial search patterns. On the other hand, M. oeconomus showed faster swimming speed, and strong thigmotaxis combined with circular swimming. M. oeconomus also scored at chance levels during the probe trial, about as poorly as mutant knockout mice considered to be deficient in spatial memory. These differences probably reflect differential styles of water maze learning rather than spatial memory deficits: C. glareolus appears to be superior in inhibiting behavior interfering with proper spatial search behavior, while M. oeconomus succeeds in escaping by using rapid circular swimming. We assume that size variations of the IIP-MF correspond to a mechanism stabilizing hippocampal processing during spatial learning or complex activities. This corresponds to the ecological lifestyle of the two species and is in line with previous observations on the role of the IIP-MF. Hippocampus 2000;10:17–30. © 2000 Wiley-Liss, Inc.

Prenatally administered oxazepam (OX) impairs adult radial maze performance in mice, possibly by permanent hippocampal changes. CDI mice were tested in swimming navigation, a sensitive indicator for hippocampal damage. Ten males and ten females were exposed to OX on fetal days 12–16 by maternal administration PO of 30 mg/kg/day and fostered at birth to untreated dams, while control mice received vehicle solution. All mice were tested at 8–9 weeks for ability to find a submerged platform in a fixed location (acquisition: 18 trials, 6 trials per day) and for capacity to re-orient towards a new platform position (reversal: 12 trials, 6 trials per day). OX mice showed a slight but significant impairment of swimming navigation during the initial part of training, as indicated by longer swimming paths during the fourth and fifth trial (day 1), an impairment due both to delayed habituation to the novel stressfull condition and acquisition of platform climbing but unrelated to navigational abilities. No treatment-dependent differences were observed in the reversal phase. During reversal, both OX and control females spent significantly more time in swimming across the location of the old platform. Unrelated to navigational performance, females showed a slightly but significantly higher swimming speed than males. Due to the absence of any navigational impairment, data suggest that prenatal exposure to oxazepam exerts long-term influence on adult learning capacities primarily through interaction with brain systems located outside the hippocampus.

Conditioned place preference (CPP) procedures using jointly visual and tactile cues (white compartment with a wide-mesh metal floor versus black compartment with a narrow-mesh floor) were employed to assess the ontogenetic pattern of cocaine reinforcing properties in outbred CD1 mice. A classical 11-day-long schedule, in which the drug experience occurred in the initially less-preferred compartment (“biased” procedure, Spyraki 1988), served to study cocaine (0, 1, 5, or 25 mg/kg IP repeated four times at 48 h intervals) during the early postweaning stage (21–32 days). The result was a fully-fledged CPP at all cocaine doses. A subsequent experiment used a shortened (4-day) “unbiased” CPP schedule (animals assigned at random to drug experience in one or the other compartment); this enabled an assessment of the ontogenetic pattern of the drug action (single treatment, same dose range) in pups of both sexes at three different developmental ages (14–17, 21–24, or 28–31 days). At the 25 mg/kg dose, CPP developed in animals of all ages, while the 5 mg/kg dose was effective only in 21–24 day pups and the 1 mg/kg dose was ineffective. No significant sex differences were found, but the use of the unbiased procedure enabled a demonstration of an interaction between treatment, age, and type of CS. At the preweaning stage, CPP was due mainly to an increased preference for the black/narrowmesh compartment, while at the early postweaning stage it consisted mainly of an increased preference for the white/wide-mesh compartment; at the late postweaning stage the cue and the treatment factor did not interact. At all ages tested cocaine induced a dose-dependent increase in locomotor activity which was much more marked at both post-weaning stages than before weaning.

Inhibition of cholinesterase (ChE) activity produced by a single acute intraperitoneal administration of dimethoate was studied in the wood mouse, Apodemus sylvaticus, and the common shrew, Sorex araneus, under laboratory conditions. ChE values from serum and whole blood were compared with those obtained from brain in order to obtain a non-destructive tool for predicting the severity of brain acetylcholinesterase (AChE) inhibition. In addition, serum and brain inhibition following oral exposure to dimethoate was also measured in the wood mouse. Normal ChE activity was higher in the brain and whole blood of the shrews than in wood mice. There was no difference between species in serum ChE activity. Exposure to dimethoate caused a dose-dependent reduction in ChE activity and there was a significant recovery in activity with increasing time after administration. In both species, serum and whole blood were more sensitive than brain for revealing organophosphate-induced ChE inhibition and serum was more sensitive than whole blood. Statistically significant relationships were defined between whole blood and brain ChE activity and between serum and brain ChE activity. Compared with serum, whole blood ChE activity was the more accurate predictor of brain AChE levels. The relationships between brain and serum ChE activity did not appear to be affected by the route of administration of the pesticide.

Abstract:  Adult male and female CD-1 mice were exposed to different SO2 concentrations (0, 5, 12, or 30 ppm) for 24 days, from 9 days before the formation of breeding pairs to pregnancy day 12–14. This exposure was near-continuous, covering about 80% of the total time indicated. The offspring of exposed dams were cross-fostered shortly after birth to dams not previously exposed. Videorecordings of the adult subjects’ activities during the first hour after the start of exposure showed marked, acute transient behavioural effects such as increase of rearing and social interactions, which were more pronounced in males than in females. Subsequent activity tests on exposure days 3, 6, and 9 showed subacute effects including a dose-dependent decrease of grooming and an increase of digging as well as changes in chamber crossing and wall-rearing which were not dose-dependent; most of these effects were more pronounced in females than in males. Food and water consumption and body weight declined in a dose-dependent fashion only after the formation of breeding pairs, when consummatory responses were enhanced in the controls. Reproductive performance as well as postnatal somatic and neurobehavioural development of the offspring (the latter assessed by an observational test battery including eight reflexes and responses) were not affected by SO2. Passive avoidance acquisition and retention at the young adult stage (60 days) and response changes produced by repeated apparatus exposure in non-reinforced animals (habituation) were similarly unaffected. Overall, the data indicate that SO2 produces transient, acute behavioural disturbances and more subtle subacute response changes in adult mice which may be due, at least partly, to a functional interference with olfactory modulation of mouse behaviour. The absence of effects on reproductive performance and neurobehavioural development of the offspring suggests that the risk to the developing organism from gestational SO2 exposure is low.

It is known that predator cues (both mammalian odor or avian vocalization) elicit marked analgesia in rodents. The present experiment used olfactory cues produced by an opportunistic rodent predator snake species (100 cc of sawdust scented by Elaphe quatuorlineata). Upon exposure to snake odor (for 30 s, 20 min, or 40 min), adult mice of both the CD-1 and DBA2 strains were assessed for tail-flick or hot-plate analgesia at different times after exposure (from 0 to 40 or 45 min, respectively). In both strains, snake odor exposure induced significant alteration in the frequencies of sniffing, self-grooming, and digging, while it inhibited habituation of locomotor activity in DBA/2 mice. No analgesia emerged with both tests as a consequence of exposure to snake odor. Results suggest that although endogenous analgesia has been demonstrated by other authors to be elicited in response to cues emanating from common and widely distributed mouse predators (such as carnivores or owls), predators such as reptiles, which under natural conditions exert a limited predatory pressure on the house mouse gene pool, may only induce fear-associated behavioral responses but cannot provide ethologically relevant stimuli triggering mouse analgesia.

Outbred CD-1 mice were exposed continuously to ozone (O3, 0.6 ppm) from 6 days prior to the formation of breeding pairs to the time of weaning of the offspring on postnatal day 22 (PND 22) or to PND 26. One half of the mice in each of eight O3and eight control litters were subjected on PND 24 to a 20-min open-field test after IP treatment by either saline or scopolamine (2 mg/kg). The remaining mice (those exposed until PND 26) were subjected on PNDs 28–31 to a conditioned place preference (CPP) test, using a short schedule with a single IP injection on PND 29 of either d-amphetamine (3.3 mg/kg) or saline. Subsequently, the saline mice of the open-field experiment were used on PND 59 for an activity test in one of the CPP apparatus compartments after IP treatment by either d-amphetamine (same dose) or saline. In addition, the saline mice of the CPP experiment underwent a multitrial, step-through passive avoidance (PA) acquisition test on PND 59 or 60, followed 24 h later by a single-trial retention test. In the absence of effects on reproductive performance (proportion of successful pregnancies, litter size, offspring viability, and sex ratio), O3offspring showed a long-lasting reduction in body weight without modification of sex differences. Ozone effects on neurobehavioral development were not large and quite selective, including: attenuation of the sex differences in several responses (rearing and sniffing in the open-field, activity in the final CPP test session); a change in response choices in the final CPP test, in the absence of a main effect on conditioning; a reduction of grooming in the activity test on PND 29; and impairment of PA acquisition limited to the initial period of training.

A new battery-operated system based on microchips has been developed for detecting free-moving, wild small mammals. An electronic identification unit connected to a portable data-logger can simultaneously accommodate up to eight detector antennae, which are positioned in the habitat of the species under study. The system can operate even in extreme weather conditions and has the capacity to distinguish and record individual mammals entering burrows or visiting artificial feeding stations. Detection events are stored in a data-logger and subsequently can be edited and analysed by many common software packages. A pilot study tested the system by monitoring the visits of three species of small mammals to artificial feeding stations. Further possible applications are discussed. J. Exp. Zool. 280:97–99, 1998. © 1998 Wiley-Liss, Inc.

Recently-developed capabilities for tracking the movements of individual birds over the course of a year or longer has provided increasing evidence for consistent individual differences in migration schedules and destinations. This raises questions about the relative importance of individual consistency versus flexibility in the evolution of migration strategies, and has implications for the ability of populations to respond to climatic change. Using geolocators, we tracked the migrations of Scopoli’s shearwaters Calonectris diomedea breeding in Linosa (Italy) across three years, and analysed timing and spatial aspects of their movements. Birds showed remarkable variation in their main wintering destination along the western coast of Africa. We found significant individual consistency in the total distance traveled, time spent in transit, and time that individuals spent in the wintering areas. We found extensive sex differences in scheduling, duration, distances and destinations of migratory journeys. We also found sex differences in the degree of individual consistency in aspects of migration behaviour. Despite strong evidence for individual consistency, which indicates that migration journeys from the same bird tended to be more similar than those of different birds, there remained substantial intra-individual variation between years. Indeed, we also found clear annual differences in departure dates, return dates, wintering period, the total distance traveled and return routes from wintering grounds back to the colony. These findings show that this population flexibly shifts migration schedules as well as routes between years in response to direct or indirect effects of heterogeneity in the environment, while maintaining consistent individual migration strategies.