A fundamental study revisited: Quantitative evidence for territory quality in oystercatchers (Haematopus ostralegus) using GPS data loggers

• A fundamental study by Ens et al. (1992, Journal of Animal Ecology, 61, 703) developed the concept of two different nest‐territory qualities in Eurasian oystercatchers (Haematopus ostralegus, L.), resulting in different reproductive successes. “Resident” oystercatchers use breeding territories close to the high‐tide line and occupy adjacent foraging territories on mudflats. “Leapfrog” oystercatchers breed further away from their foraging territories. In accordance with this concept, we hypothesized that both foraging trip duration and trip distance from the high‐tide line to the foraging territory would be linearly related to distance between the nest site and the high tide line. We also expected tidal stage and time of day to affect this relationship.
• The former study used visual observations of marked oystercatchers, which could not be permanently tracked. This concept model can now be tested using miniaturized GPS devices able to record data at high temporal and spatial resolutions.
• Twenty‐nine oystercatchers from two study sites were equipped with GPS devices during the incubation periods (however, not during chick rearing) over 3 years, providing data for 548 foraging trips. Trip distances from the high‐tide line were related to distance between the nest and high‐tide line. Tidal stage and time of day were included in a mixing model.
• Foraging trip distance, but not duration (which was likely more impacted by intake rate), increased with increasing distance between the nest and high‐tide line. There was a site‐specific effect of tidal stage on both trip parameters. Foraging trip duration, but not distance, was significantly longer during the hours of darkness.
• Our findings support and additionally quantify the previously developed concept. Furthermore, rather than separating breeding territory quality into two discrete classes, this classification should be extended by the linear relationship between nest‐site and foraging location. Finally, oystercatcher′s foraging territories overlapped strongly in areas of high food abundance.

     

Wildlife tracking data management: a new vision

To date, the processing of wildlife location data has relied on a diversity of software and file formats. Data management and the following spatial and statistical analyses were undertaken in multiple steps, involving many time-consuming importing/exporting phases. Recent technological advancements in tracking systems have made large, continuous, high-frequency datasets of wildlife behavioural data available, such as those derived from the global positioning system (GPS) and other animal-attached sensor devices. These data can be further complemented by a wide range of other information about the animals'' environment. Management of these large and diverse datasets for modelling animal behaviour and ecology can prove challenging, slowing down analysis and increasing the probability of mistakes in data handling. We address these issues by critically evaluating the requirements for good management of GPS data for wildlife biology. We highlight that dedicated data management tools and expertise are needed. We explore current research in wildlife data management. We suggest a general direction of development, based on a modular software architecture with a spatial database at its core, where interoperability, data model design and integration with remote-sensing data sources play an important role in successful GPS data handling.     

Sex-specific foraging behaviour in a seabird with reversed sexual dimorphism: the red-footed booby

Most hypotheses attempting to explain the evolution of reversed sexual dimorphism (RSD) assume that size-related differences in foraging ability are of prime importance, but the studies on sex-specific differences in foraging behaviour remain scarce. We compare the foraging behaviour of males and females in a seabird species with a RSD by using several miniaturised activity and telemetry loggers. In red-footed boobies males are 5% smaller and 15% lighter than females, but have a longer tail than females. Both sexes spend similar time on the nest while incubating or brooding. When foraging at sea, males and females spend similar time foraging in oceanic waters, forage in similar areas, spend similar proportion of their foraging trip in flight, and feed on similar prey—flying fishes and flying squids—of similar size. However, compared to males, females range farther during incubation (85 km vs. 50 km), and furthermore feed mostly at the extremity of their foraging trip, whereas males actively forage throughout the trip. Males are much more active than females, landing and diving more often. During the study period, males lost mass, whereas females showed no significant changes. These results indicate that males and females of the red-footed boobies differ in several aspects in their foraging behaviour. Although some differences found in the study may be the direct result of the larger size of females, that is, the slightly higher speeds and deeper depths attained by females, others indicate clearly different foraging strategies between the sexes. The smaller size and longer tail of males confer them a higher agility, and could allow them to occupy a foraging niche different from that of females. The higher foraging effort of males related to its different foraging strategy is probably at the origin of the rapid mass loss of males during the breeding period. These results suggest that foraging differences are probably the reason for the differential breeding investment observed in boobies, and are likely to be involved in the evolution and maintenance of RSD.     

Perching of Tengmalm's Owl (Aegolius funereus) Nestlings at the Nest Box Entrance: Effect of Time of the Day,Age, Wing Length and Body Weight

The behaviour of the nestlings of nocturnal cavity-nesting species has relatively rarely been studied in detail because of problems connected with use of the technical devices required to provide long-term monitoring of individuals. However, long-term observation of nestling behaviour is crucial in order to identify different types of behaviour which may be caused by sibling competition at the end of nesting period. We studied behaviour of 43 Tengmalm''s owl (Aegolius funereus) nestlings at 14 nests using a camera and a chip system. The nestlings perched at the nest box entrance from an average age of 28 days from hatching (range 24–34 days) until fledging, spending around 2 hours per day here in total, in periods ranging from a few seconds to 147 min (7.6±10.9 min, mean ± SD). We found that individual duration of perching at the nest box entrance was significantly influenced by nestlings'' age and wing length and that the duration of perching at the nest box entrance significantly decreased with time of night. However, during daylight hours, time of day had no effect on either probability or duration of nestlings'' perching. We suggest daylight perching at the nest box entrance results from nestlings'' preparation for fledging, while individuals perching here during the night may gain an advantageous position for obtaining food from the parents; another possibility at all times of day is that nestlings can reaffirm their social dominance status by monopolizing the nest box entrance.     

Off‐nest behaviour in a biparentally incubating shorebird varies with sex,time of day and weather

Biparental incubation is a form of cooperation between parents, but it is not conflict‐free because parents trade off incubation against other activities (e.g. self‐maintenance, mating opportunities). How parents resolve such conflict and achieve cooperation remains unknown. To understand better the potential for conflict, cooperation and the constraints on incubation behaviour, investigation of the parents' behaviour, both during incubation and when they are off incubation‐duty, is necessary. Using a combination of automated incubation‐monitoring and radiotelemetry we simultaneously investigated the behaviours of both parents in the biparentally incubating Semipalmated Sandpiper Calidris pusilla, a shorebird breeding under continuous daylight in the high Arctic. Here, we describe the off‐nest behaviour of 32 off‐duty parents from 17 nests. Off‐duty parents roamed on average 224 m from their nest, implying that direct communication with the incubating partner is unlikely. On average, off‐duty parents spent only 59% of their time feeding. Off‐nest distance and behaviour (like previously reported incubation behaviour) differed between the sexes, and varied with time and weather. Males roamed less far from the nest and spent less time feeding than did females. At night, parents stayed closer to the nest and tended to spend less time feeding than during the day. Further exploratory analyses revealed that the time spent feeding increased over the incubation period, and that at night, but not during the day, off‐duty parents spent more time feeding under relatively windy conditions. Hence, under energetically stressful conditions, parents may be forced to feed more. Our results suggest that parents are likely to conflict over the favourable feeding times, i.e. over when to incubate (within a day or incubation period). Our study also indicates that Semipalmated Sandpiper parents do not continuously keep track of each other to optimize incubation scheduling and, hence, that the off‐duty parent's decision to remain closer to the nest drives the length of incubation bouts.     

So close and yet so different: The importance of considering temporal dynamics to understand habitat selection

Habitat selection of animals is influenced by spatial heterogeneity as well as temporal environmental dynamics. In addition, human activities potentially have severe influences on the habitat selection of animals, often resulting in more nocturnal behavior. We investigated seasonal and circadian habitat selection patterns of red deer (Cervus elaphus) on a military training area in Bavaria (Germany). Individual deer ranged on two neighboring, but non-overlapping sites differing in landscape composition and human activity. Using GPS telemetry data, we visually investigated selection patterns and then fitted step-selection functions to assess multiple approaches to account for temporal (i.e., diel and seasonal) effects and for the impact of habitat conditions on selection. We first showed that the way in which time of day is considered in step-selection functions is essential for obtaining ecologically meaningful results, and that the usual ways of including time (i.e., either based on clock-time or based on night vs. day categories) can lead to incomplete or misleading conclusions. Furthermore, we found that individuals followed either circadian or seasonal habitat selection patterns, depending on the site they inhabited. This can be explained by differences in disturbance between the two sites. Except in winter, individuals selected for open habitats during the night irrespective of human activity level, but only individuals from the more disturbed site selected for covered habitats during the day. Our results highlight the importance of carefully considering the appropriate temporal scale for habitat selection analyses. Our findings also indicate that red deer are not a crepuscular or nocturnal species per se, as is often observed in human-dominated landscapes. Instead, our results imply that nocturnality in red deer is an effect of adaption to human activities.     

Modeling activity patterns of wildlife using time‐series analysis

The study of wildlife activity patterns is an effective approach to understanding fundamental ecological and evolutionary processes. However, traditional statistical approaches used to conduct quantitative analysis have thus far had limited success in revealing underlying mechanisms driving activity patterns. Here, we combine wavelet analysis, a type of frequency‐based time‐series analysis, with high‐resolution activity data from accelerometers embedded in GPS collars to explore the effects of internal states (e.g., pregnancy) and external factors (e.g., seasonal dynamics of resources and weather) on activity patterns of the endangered giant panda (Ailuropoda melanoleuca). Giant pandas exhibited higher frequency cycles during the winter when resources (e.g., water and forage) were relatively poor, as well as during spring, which includes the giant panda's mating season. During the summer and autumn when resources were abundant, pandas exhibited a regular activity pattern with activity peaks every 24 hr. A pregnant individual showed distinct differences in her activity pattern from other giant pandas for several months following parturition. These results indicate that animals adjust activity cycles to adapt to seasonal variation of the resources and unique physiological periods. Wavelet coherency analysis also verified the synchronization of giant panda activity level with air temperature and solar radiation at the 24‐hr band. Our study also shows that wavelet analysis is an effective tool for analyzing high‐resolution activity pattern data and its relationship to internal and external states, an approach that has the potential to inform wildlife conservation and management across species.     

Temporal asynchrony and spatial co-occurrence with the host: the foraging patterns of Nemka viduata, a parasitoid of digger wasps (Hymenoptera: Mutillidae and Crabronidae)

Studies which quantitatively analyse how aculeate parasitoids exploit their window of opportunity to find and attack a host are scarce, despite the recognized importance of parasitic pressure as a driving force that promotes aggregate nesting in their hosts. We have studied the activity and behaviour of the velvet ant Nemka viduata, an ectoparasitoid of immature stages of the digger wasp Stizus continuus. Due to the resource exploited by the parasitoid (mature larvae and prepupae), and in general agreement with basic optimal foraging theory, we expected a major activity at late stages of the host seasonal provisioning period, an independence from the host daily provisioning patterns and a spatial positive association with host nest density. In accordance with these predictions, during the season, the parasitoid resulted was more active at the end of the host provisioning period, and across the day, it showed an inverse quadratic pattern of activity, in contrast to the positive one shown by the host. Thus, at both temporal scales, N. viduata activity was highly asynchronous with that of the host. At a spatial scale, however, the activity of the velvet ants was correlated with host nest density, although there is weak evidence suggesting that areas of high host density suffered from a higher rate of parasitism. Multivariate analyses confirmed a number of relevant factors associated with velvet ants’ activity, including nest density (positive), air temperature and the hour of the day (both negative). In addition, the activity of both male S. continuus and male N. viduata entered in the models in association with female parasitoid’s activity, probably because of their mating strategy.     

Spatial and Temporal Activity Patterns of the Free-Living Giant Mole-Rat (Fukomys mechowii), the Largest Social Bathyergid

Despite the considerable attention devoted to the biology of social species of African mole-rats (Bathyergidae, Rodentia), knowledge is lacking about their behaviour under natural conditions. We studied activity of the largest social bathyergid, the giant mole-rat Fukomys mechowii, in its natural habitat in Zambia using radio-telemetry. We radio-tracked six individuals during three continuous 72-h sessions. Five of these individuals, including a breeding male, belonged to a single family group; the remaining female was probably a solitary disperser. The non-breeders of the family were active (i.e. outside the nest) 5.8 hours per 24h-day with the activity split into 6.5 short bouts. The activity was more concentrated in the night hours, when the animals also travelled longer distances from the nest. The breeding male spent only 3.2 hours per day outside the nest, utilizing less than 20% of the whole family home range. The dispersing female displayed a much different activity pattern than the family members. Her 8.0 hours of outside-nest activity per day were split into 4.6 bouts which were twice as long as in the family non-breeders. Her activity peak in the late afternoon coincided with the temperature maximum in the depth of 10 cm (roughly the depth of the foraging tunnels). Our results suggest that the breeding individuals (at least males) contribute very little to the work of the family group. Nevertheless, the amount of an individual''s activity and its daily pattern are probably flexible in this species and can be modified in response to actual environmental and social conditions.     

A Test of the Effect of Male Song on Female Nesting Behaviour in the Serin (Serinus serinus): a Field Playback Experiment

It is well established, through laboratory experiments, that male song in birds can stimulate female reproductive activity, affecting their behaviour and physiology, such as follicular growth, nest building and egg‐laying. However no clear demonstration has yet been provided that this effect works under natural conditions. Previous work in natural populations of serins showed that female nest‐building behaviour correlated with male singing time. Furthermore male serin song peaked exactly in the day that rapid follicular growth was estimated to start in females, suggesting that in this species song may also serve to stimulate the female's reproductive development. Direct causal evidence, however, was lacking. We conducted field playback experiments to investigate how song can influence female nesting activity during nest building. Our results show that females who listened daily to playbacks of serin songs, during the nest‐building stage, spent more time nest building than females that were not exposed to additional songs. Moreover, the singing behaviour of the mated males was not affected by the playbacks, suggesting that the song playback treatment had a direct positive effect on female nesting behaviour.     

Chemical regulation of body feather microbiota in a wild bird

The microbiota has a broad range of impacts on host physiology and behaviour, pointing out the need to improve our comprehension of the drivers of host–microbiota composition. Of particular interest is whether the microbiota is acquired passively, or whether and to what extent hosts themselves shape the acquisition and maintenance of their microbiota. In birds, the uropygial gland produces oily secretions used to coat feathers that have been suggested to act as an antimicrobial defence mechanism regulating body feather microbiota. However, our comprehension of this process is still limited. In this study, we for the first time coupled high‐throughput sequencing of the microbiota of both body feathers and the direct environment (i.e., the nest) in great tits with chemical analyses of the composition of uropygial gland secretions to examine whether host chemicals have either specific effects on some bacteria or nonspecific broad‐spectrum effects on the body feather microbiota. Using a network approach investigating the patterns of co‐occurrence or co‐exclusions between chemicals and bacteria within the body feather microbiota, we found no evidence for specific promicrobial or antimicrobial effects of uropygial gland chemicals. However, we found that one group of chemicals was negatively correlated to bacterial richness on body feathers, and a higher production of these chemicals was associated with a poorer body feather bacterial richness compared to the nest microbiota. Our study provides evidence that chemicals produced by the host might function as a nonspecific broad‐spectrum antimicrobial defence mechanism limiting colonization and/or maintenance of bacteria on body feathers, providing new insight about the drivers of the host's microbiota composition in wild organisms.     

Assessing parental effort in a Neotropical parrot: a comparison of methods

Various behavioural or body condition indices are frequently used to measure avian parental effort. To determine which of the indices provide meaningful short-term assessments of parental effort, we used four of them concurrently on breeding green-rumped parrotlets, Forpus passerinus, and then compared the results with field metabolic rate (FMR) measurements obtained using the doubly labelled water (DLW) technique. Nest provisioning rate correlated significantly with FMR among both males and females, while proportion of time away from the nest was correlated with FMR in females but not in males. Adult mass change during the breeding cycle and feeding latency were both unrelated to FMR. Our results suggest researchers should be cautious in assuming that any indirect method of quantifying parental effort is reliable for a particular species. We also tested whether the relatively invasive DLW protocol causes potentially confounding changes in study animals' subsequent behaviour. Paired observations before and after DLW injection showed no measurable changes in parrotlet nest attendance patterns or nest provisioning rate. Copyright 1999 The Association for the Study of Animal Behaviour.     

Behaviour of female common cuckoos, Cuculus canorus, in the vicinity of host nests before and during egg laying: a radiotelemetry study

We radiotracked 13 common cuckoo females in the southeastern part of the Czech Republic. Seven females laid eggs in the nests of reed warblers, Acrocephalus scirpaceus, sedge warblers, A. schoenobaenus, and marsh warblers, A. palustris. We observed 53 nest visits, of which 26 involved egg laying. Cuckoos spent significantly more time within 50 m of the host nest on the laying day than on the 5 prelaying days. The vantage point used when parasitizing or visiting a nest was on average four times further from the nest than the closest possible vantage point, but there was a positive correlation between these two distances. Cuckoos spent on average 20 min observing host nests from their vantage points before they visited a nest. Comparison of cuckoos' visits to host nests with and without egg laying revealed no significant differences in the duration of visits or in other measures of behaviour. There was significant variation in behaviour between cuckoos, particularly in the time of day when eggs were laid in host nests. This variation can be attributed to the strong, but not absolute, host and habitat specificity of individuals. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Effects of back-mounted biologgers on condition,diving and flight performance in a breeding seabird

Biologging devices are providing detailed insights into the behaviour and movement of animals in their natural environments. It is usually assumed that this method of gathering data does not impact on the behaviour observed. However, potential negative effects on birds have rarely been investigated before field-based studies are initiated. Seabirds which both fly and use pursuit diving may be particularly sensitive to increases in drag and load resulting from carrying biologging devices. We studied chick-rearing adult common guillemots Uria aalge equipped with and without back-mounted GPS tags over short deployments of a few days. Concurrently guillemots carried small leg-mounted TDR devices (time-depth recorders) providing activity data throughout. Changes in body mass and breeding success were followed for device equipped and control guillemots. At the colony level guillemots lost body mass throughout the chick-rearing period. When-equipped with the additional GPS tag, the guillemots lost mass at close to twice the rate they did when equipped with only the smaller leg-mounted TDR device. The elevated mass loss suggests an impact on energy expenditure or foraging performance. When equipped with GPS tags diving performance, time-activity budgets and daily patterns of activity were unchanged, yet dive depth distributions differed. We review studies of tag-effects in guillemots Uria sp. finding elevated mass loss and reduced chick-provisioning to be the most commonly observed effects. Less information is available for behavioural measures, and results vary between studies. In general, small tags deployed over several days appear to have small or no measurable effect on the behavioural variables commonly observed in most guillemot tagging studies. However, there may still be impacts on fitness via physiological effects and/or reduced chick-provisioning, while more detailed measures of behaviour (e.g. using accelerometery) may reveal effects on diving and flight performance.     

Global positioning system data analysis: velocity ranges and a new definition of sprinting for field sport athletes

Global positioning system (GPS) technology has improved the speed, accuracy, and ease of time-motion analyses of field sport athletes. The large volume of numerical data generated by GPS technology is usually summarized by reporting the distance traveled and time spent in various locomotor categories (e.g., walking, jogging, and running). There are a variety of definitions used in the literature to represent these categories, which makes it nearly impossible to compare findings among studies. The purpose of this work was to propose standard definitions (velocity ranges) that were determined by an objective analysis of time-motion data. In addition, we discuss the limitations of the existing definition of a sprint and present a new definition of sprinting for field sport athletes. Twenty-five GPS data files collected from 5 different sports (men's and women's field hockey, men's and women's soccer, and Australian Rules Football) were analyzed to identify the average velocity distribution. A curve fitting process was then used to determine the optimal placement of 4 Gaussian curves representing the typical locomotor categories. Based on the findings of these analyses, we make recommendations about sport-specific velocity ranges to be used in future time-motion studies of field sport athletes. We also suggest that a sprint be defined as any movement that reaches or exceeds the sprint threshold velocity for at least 1 second and any movement with an acceleration that occurs within the highest 5% of accelerations found in the corresponding velocity range. From a practical perspective, these analyses provide conditioning coaches with information on the high-intensity sprinting demands of field sport athletes, while also providing a novel method of capturing maximal effort, short-duration sprints.     

Nest desertion: a trade-off between current and future reproduction

Life history theory predicts that parents should desert a reproductive attempt if the costs of rearing this brood exceed the expected benefits. Thus, if the value of the current breeding attempt is reduced, for example through an unexpected reduction in size, parents are expected to reconsider whether it is worth continuing investing in their brood. With regard to nest desertion behaviour two predictions can be made: individuals are (1) more likely to desert if the reduction in clutch size is large and (2) less likely to desert if the reduction is at a late stage of breeding. We investigated the threshold at which nest desertion takes place by experimentally reducing great tit, Parus major, clutches to different sizes and at different stages of the incubation period. The results were in accordance with the predictions: clutch desertion rates were negatively related to the number of eggs that remained in the nest, and nest desertion was less likely nearer the end of the incubation period. In addition, we estimated the fitness consequences of nest desertion behaviour. For this purpose we made one group of birds desert in favour of a replacement clutch and another group rear a reduced brood. The latter were more likely to produce a second clutch after the first-brood fledglings had left the nest. As a consequence, the number of fledglings produced over the entire breeding season did not differ between the two experimental groups. We also counted the number of recruits and breeding adults in the following breeding season and found that the experimental groups did not differ in local recruitment and adult survival. Therefore, the results did not indicate that parents improved their fitness by deserting a reduced clutch.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .     

Contrast in edge vegetation structure modifies the predation risk of natural ground nests in an agricultural landscape

Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depend on edge contrast, (ii) that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk.     

Nesting and post-fledging predation risk influence diel patterns of songbird fledging

Among stages of avian ontogeny, the act of nest departure or fledging is an abrupt transition into a new environment and a major leap toward independence for offspring. In altricial birds, the timing (i.e. time of day) of fledging is notable in that many species tend to fledge early in the morning. Past studies have proposed nest predation as a key factor driving birds to fledge earlier in the morning (the ‘survival hypothesis’), whereby offspring avoid peak times of nest predation that occur later in the day. A natural extension of this hypothesis is the predation of offspring post-fledging, whereby offspring are also timing their fledging with future survival prospects outside of the nest. However, few studies have investigated fledging behaviour in the context of both nesting and post-fledging predation. To help fill this knowledge gap, we investigated factors driving the timing and duration of fledging across six songbird species in the context of offspring predation: daily nest mortality, post-fledging mortality and diel patterns of nest predation risk. We found that > 60% of songbirds fledged early in the morning, whereas the peaks in nest predation risk occurred several hours post-fledging. Furthermore, species under greater risk of nest predation fledged earlier in the day and in closer succession to their siblings. Parameters of post-fledging mortality were poor predictors of fledging timing, but individuals from broods of species under higher risk of post-fledging mortality fledged in closer succession to their siblings. These results provide evidence in support of the survival hypothesis, and suggest that songbirds fledge in the morning to avoid peak times of nest predation risk that occur later in the day (~ 8 h after civil dawn). Such results corroborate past research highlighting predation on dependent offspring as a key factor driving variation in life histories across animal taxa; however, estimates of post-fledging mortality suggest that nest predation alone does not fully explain variation in fledging behaviour among species. Future research is therefore needed to investigate the contribution of other factors, such as energetics, parent–offspring conflict and diel patterns of post-fledging survival, which may help to mediate diel patterns of fledging within and among songbird species.     

Daily Activity and Nest Occupation Patterns of Fox Squirrels (Sciurus niger) throughout the Year

The authors investigated the general activity and nest occupation patterns of fox squirrels in a natural setting using temperature-sensitive data loggers that measure activity as changes in the microenvironment of the animal. Data were obtained from 25 distinct preparations, upon 14 unique squirrels, totaling 1385 recording days. The animals were clearly diurnal, with a predominantly unimodal activity pattern, although individual squirrels occasionally exhibited bimodal patterns, particularly in the spring and summer. Even during the short days of winter (9 hours of light), the squirrels typically left the nest after dawn and returned before dusk, spending only about 7 hours out of the nest each day. Although the duration of the daily active phase did not change with the seasons, the squirrels exited the nest earlier in the day when the days became longer in the summer and exited the nest later in the day when the days became shorter in the winter, thus tracking dawn along the seasons. During the few hours spent outside the nest each day, fox squirrels seemed to spend most of the time sitting or lying. These findings suggest that fox squirrels may have adopted a slow life history strategy that involves long periods of rest on trees and short periods of ground activity each day.