Vergesellschaftung als Verhaltensbereicherung im Zoo – Soziale Interaktion und Raumnutzung bei Orang-Utans,Hulmans und Kurzkrallenottern in der Zoom Erlebniswelt Gelsenkirchen

Keeping different species together is getting more and more common in zoos, because it can entail several behavioural enrichment factors for the animals as long as the enclosure meets the requirements of all species and a suitable composition of animals is living in the mix. The aim of this study is to evaluate a community of Sumatran orangutans (Pongo abelii), northern plains grey langurs (Semnopithecus entellus) and Asian small-clawed otters (Aonyx cinerea) in the Zoological Garden of Gelsenkirchen.The behavioural monitoring of the animals reveals that the orangutans spend less time with feeding behaviour and locomotion than free ranging orangutans, whereas the percentage of resting periods is much higher. This difference is probably caused by the easy availability of food. The northern plains grey langurs show ethograms whose proportions are very similar to those of free ranging grey langurs in literature. In both species the juvenile individuals have higher activity levels than the adult animals.The analysis of the spatial use of the enclosure by the orangutans reveals that they use about half of the area and prefer places at the ground for resting. On an average the orangutans spend around 50% of the monitored situations on the ground which is a high level for an arboreal living species. The time spent on the ground is distinctly lower in orangutans reared by their parents than in hand reared individuals which are probably affected by humans. Another influencing point is the sex. Adult male orangutans spend more time on the ground. This is a fact which is also known from free ranging animals. Related to their environment free ranging northern plains grey langurs show a high adaptability and the individuals in the zoo use about 70% of the enclosure and use frequently all structuring elements like trees, roots and ropes. Like the orangutans the grey langurs have preferred areas in the enclosure where they spend their resting periods with grooming, lactating and the feeding periods. Generally, the Asian small-clawed otters spend less time in the enclosure than the monkeys and use less than one third of the area.Most of the time free ranging orangutans live solitarily and thus it was predictable that there is only a fraction of intraspecific interactions between orangutans whereas the percentage of interactions between langurs is higher. The northern plains grey langurs live in harem troops and social interactions are more than 40% of the zoo langur's ethogram on an average. Asian small-clawed otters are also highly social animals and intraspecific contacts take place very often.The analysis of the monitored interspecific interactions between all species reveals that the juvenile animals of both primate species have distinct more interspecific contacts than the adult animals. In most cases the interactions are positive or playful contacts. Especially between a 12-year-old female orang-utan and one of the juvenile langurs friendly interactions with body contact were monitored often. Between the adult animals agonistic contacts or submission are most common. The Asian small-clawed otters are very interested in the orangutans and often approach towards them to have a sniff or pull their hair.The community of all three species is quite harmonious and serves as behavioural enrichment for all individuals. For the visitors the mixed enclosure is a benefit as well.     

Mass regulation in response to predation risk can indicate population declines

In theory, survival rates and consequent population status might be predictable from instantaneous behavioural measures of how animals prioritize foraging vs. avoiding predation. We show, for the 30 most common small bird species ringed in the UK, that one quarter respond to higher predation risk as if it is mass-dependent and lose mass. Half respond to predation risk as if it only interrupts their foraging and gain mass thus avoiding consequent increased starvation risk from reduced foraging time. These mass responses to higher predation risk are correlated with population and conservation status both within and between species (and independently of foraging habitat, foraging guild, sociality index and size) over the last 30 years in Britain, with mass loss being associated with declining populations and mass gain with increasing populations. If individuals show an interrupted foraging response to higher predation risk, they are likely to be experiencing a high quality foraging environment that should lead to higher survival. Whereas individuals that show a mass-dependent foraging response are likely to be in lower quality foraging environments, leading to relatively lower survival.     

Brain size, innovative propensity and migratory behaviour in temperate Palaearctic birds

The evolution of migration in birds remains an outstanding, unresolved question in evolutionary ecology. A particularly intriguing question is why individuals in some species have been selected to migrate, whereas in other species they have been selected to be sedentary. In this paper, we suggest that this diverging selection might partially result from differences among species in the behavioural flexibility of their responses to seasonal changes in the environment. This hypothesis is supported in a comparative analysis of Palaearctic passerines. First, resident species tend to rely more on innovative feeding behaviours in winter, when food is harder to find, than in other seasons. Second, species with larger brains, relative to their body size, and a higher propensity for innovative behaviours tend to be resident, while less flexible species tend to be migratory. Residence also appears to be less likely in species that occur in more northerly regions, exploit temporally available food sources, inhabit non-buffered habitats and have smaller bodies. Yet, the role of behavioural flexibility as a response to seasonal environments is largely independent of these other factors. Therefore, species with greater foraging flexibility seem to be able to cope with seasonal environments better, while less flexible species are forced to become migratory.     

Adaptive regulation of body reserves in reindeer, Rangifer tarandus: a feeding experiment

The costs and benefits of body reserves fluctuate according to predictable factors such as season and life-cycle stage. Theory suggests that individuals at any time should regulate their body reserves according to the current balance between costs and benefits. Most studies on adaptive body mass regulation have been done on small passerine birds. In large vertebrates the costs associated with body reserves are assumed to be small and the reserves of these species are therefore thought to be dictated by environmental limitations. In this study we present experimental evidence for adaptive body mass regulation in female semi-domesticated reindeer ( Rangifer t. tarandus ). The risk of starvation in this species is highest in late winter. During snow melt this risk is reduced and the females should direct their effort towards the protection of their new born calf. To test how these seasonal and life-cycle changes are related to body mass regulation, we conducted a crossed experiment with two treatments where females were fed ad libitum during winter and spring respectively. During winter, the females from the fed group gained on average 12% of their initial body weight while the females from natural pastures lost on average 6% of their initial body weight. This strong response to winter feeding had no effect on reproductive performance, and the previously fed females lost their excess of body reserves during feeding in spring. This suggests that body reserves during winter primarily is used as an insurance against stochastic periods of starvation and that the females regulate their body reserves down to a set point in spring when the risk is reduced. We found however a positive correlation between initial female body weight and reproductive performance suggesting a close relationship between body weight and intrinsic individual qualities.     

Time budgets of Snow Geese Chen caerulescens and Ross's Geese Chen rossii in mixed flocks: implications of body size, ambient temperature and family associations

Body size affects foraging and forage intake rates directly via energetic processes and indirectly through interactions with social status and social behaviour. Ambient temperature has a relatively greater effect on the energetics of smaller species, which also generally are more vulnerable to predator attacks than are larger species. We examined variability in an index of intake rates and an index of alertness in Lesser Snow Geese Chen caerulescens caerulescens and Ross's Geese Chen rossii wintering in southwest Louisiana. Specifically we examined variation in these response variables that could be attributed to species, age, family size and ambient temperature. We hypothesized that the smaller Ross's Geese would spend relatively more time feeding, exhibit relatively higher peck rates, spend more time alert or raise their heads up from feeding more frequently, and would respond to declining temperatures by increasing their proportion of time spent feeding. As predicted, we found that Ross's Geese spent more time feeding than did Snow Geese and had slightly higher peck rates than Snow Geese in one of two winters. Ross's Geese spent more time alert than did Snow Geese in one winter, but alert rates differed by family size, independent of species, in contrast to our prediction. In one winter, time spent foraging and walking was inversely related to average daily temperature, but both varied independently of species. Effects of age and family size on time budgets were generally independent of species and in accordance with previous studies. We conclude that body size is a key variable influencing time spent feeding in Ross's Geese, which may require a high time spent feeding at the expense of other activities.     

捕食风险对不同饥饿状态下艾虎取食行为的影响

在室内条件下,将大鵟作为艾虎的天敌动物,通过双通道选择实验确定6 只成体艾虎在3 个捕食风险水平和4 种饥饿状态条件下的取食行为,探讨艾虎在取食过程中对饥饿风险与捕食风险的权衡策略。研究结果表明:在无捕食风险存在时,艾虎被剥夺食物0 d 和1 d 后对食物量不同的两个斑块中的取食量和利用频次均无明显不同(P > 0. 05),但对高食物量斑块的利用时间均明显高于低食物量斑块的(P <0.05),而艾虎被剥夺食物2 d和3 d后对高食物量斑块中的取食量和利用时间均明显高于低食物量斑块中的(P < 0.05),但在利用频次上均无明显差异(P > 0.05)。在面临低风险时,艾虎在4 种饥饿状态下均只利用无天敌动物存在的低食物量斑块,而基本不利用有天敌动物存在的高食物量斑块。在面临高风险时,艾虎不得不利用有天敌动物存在的食物斑块,被剥夺食物0 d 时艾虎对无风险、无食物量斑块的利用时间基本相同于对高风险、有食物量斑块的利用时间(P>0.05),而被剥夺食物1d、2 d 和3 d 后艾虎对高风险、有食物量斑块的利用时间明显高于无风险、无食物量斑块的(P< 0. 05)。在相同风险条件下,随着饥饿程度增加,艾虎在斑块中的取食量均明显增加(P< 0.05),而对斑块的利用时间和利用频次明显降低(P<0.05)。在相同的饥饿状态下,不同风险水平时,艾虎在斑块中的取食量无明显的差异(P>0.05),但在低风险和高风险时对斑块的利用时间和频次均明显低于无风险时的(P <0.05)。以上结果说明艾虎能够根据食物摄取率和自身的能量需求在捕食风险和饥饿风险之间做出权衡,当饥饿风险小于捕食风险时,艾虎趋于躲避捕食风险,当饥饿风险大于捕食风险时,艾虎趋于面对捕食风险,所采用的取食策略是减少活动时间和能量消耗,最大程度地提高单位时间内获得的能量。     

A tradeoff between perceived predation risk and energy conservation revealed by an immune challenge experiment

Energy is typically a limiting factor for animals during boreal winters, when low temperatures increase the cost of thermoregulation at the same times as short day‐lengths and snow cover constrain foraging opportunities. Under these circumstances animals use a suite of behavioural and physiological adaptations to avoid overnight starvation. However, it is poorly understood how such strategies are affected by increased energy demands from other physiological systems. Thus, we used free‐ranging blue tits, Cyanistes caeruleus, to test if competing demands for energy (here induced by a non‐inflammatory, antibody‐mediated immune challenge) would affect nocturnal body temperature (a predictor of energy expenditure in small animals) and energy‐saving nest box roosting behaviour. We also assessed if the immune challenge incurred long‐term survival costs. We found no evidence that body temperature regulation differed between immune‐challenged and saline‐injected birds. Nor did the immune challenge reduce survival to the next breeding season. However, old (second winter or older) immune‐challenged birds continued roosting in nest boxes to a larger extent at the peak immune response, despite increased perceived predation risk induced by the preceding capture and immunization. In contrast, old control birds were less prone to roost in nest boxes after capture and saline injection. This difference was less pronounced in young (first winter) birds. We interpret the increased risk‐taking behaviour in immune‐challenged birds as a consequence of a higher need for exploiting the thermal benefits of nest box roosting to reduce energy loss. This suggests that resource deficiency might be a stronger predictor of overnight survival than the threat of nocturnal predation in this system. As such, our study provides insights into the classic tradeoff between starvation and predation risk, in suggesting that priority is given to minimizing the risk of starvation in situations where both starvation and predation risks increase during cold winter nights.     

Group size elicits specific physiological response in herbivores

With increasing group size, individuals commonly spend less time standing head-up (scanning) and more time feeding. In small groups, a higher predation risk is likely to increase stress, which will be reflected by behavioural and endocrine responses. However, without any predator cues, we ask how the predation risk is actually processed by animals as group size decreases. We hypothesize that group size on its own acts as a stressor. We studied undisturbed groups of sheep under controlled pasture conditions, and measured in situ the cortisol and vigilance responses of identified individuals in groups ranging from 2 to 100 sheep. Both vigilance and average cortisol concentration decreased as group size increased. However, the cortisol response varied markedly among individuals in small groups, resulting in a lack of correlation between cortisol and vigilance responses. Further experiments are required to explore the mechanisms that underlie both the decay and the convergence of individual stress in larger groups, and whether these mechanisms promote adaptive anti-predator responses.     

Turning Shy on a Winter's Day: Effects of Season on Personality and Stress Response in Microtus arvalis

Animal personalities are by definition stable over time, but to what extent they may change during development and in adulthood to adjust to environmental change is unclear. Animals of temperate environments have evolved physiological and behavioural adaptations to cope with the cyclic seasonal changes. This may also result in changes in personality: suites of behavioural and physiological traits that vary consistently among individuals. Winter, typically the adverse season challenging survival, may require individuals to have shy/cautious personality, whereas during summer, energetically favourable to reproduction, individuals may benefit from a bold/risk‐taking personality. To test the effects of seasonal changes in early life and in adulthood on behaviours (activity, exploration and anxiety), body mass and stress response, we manipulated the photoperiod and quality of food in two experiments to simulate the conditions of winter and summer. We used the common voles (Microtus arvalis) as they have been shown to display personality based on behavioural consistency over time and contexts. Summer‐born voles allocated to winter conditions at weaning had lower body mass, a higher corticosterone increase after stress and a less active, more cautious behavioural phenotype in adulthood compared to voles born in and allocated to summer conditions. In contrast, adult females only showed plasticity in stress‐induced corticosterone levels, which were higher in the animals that were transferred to the winter conditions than to those staying in summer conditions. These results suggest a sensitive period for season‐related behavioural plasticity in which juveniles shift over the bold–shy axis.     

The effects of starvation and repeated disturbance on mass loss,pit construction,and spatial pattern in a trap‐building predator

1. Starvation tolerance is an important trait for animals, as most will encounter starvation within their lifetime. Sit‐and‐wait predators are better adapted to starvation owing to their naturally low encounter rate with prey. 2. Starvation tolerance was studied under three levels of disturbance of wormlion larvae, a strict sit‐and‐wait predator that constructs pits. 3. Frequently disturbed wormlions constructed pits less often, and larger individuals continued to construct pits more frequently than smaller ones. It was expected that a high disturbance level would lead to a high rate of mass loss, however, surprisingly, the rate of mass loss was not higher for the frequently disturbed group. This suggests that the energetic cost of pit construction and maintenance is not as high as previously suggested for other pit‐building predators. 4. Larger individuals tolerated starvation better, in losing a lower proportion of their initial body mass and having higher chances of survival throughout the experiment. 5. The effect of starvation on the distance to neighbours was also investigated, and starved individuals were expected to maximise this distance in order to avoid interference competition. However, wormlions were usually clumped, and starvation or feeding had no effect on the pits' spatial pattern, suggesting that interference competition plays a minor role in this species. 6. Generally, wormlion larvae demonstrated a high starvation tolerance and low mortality rates even after 9 weeks of starvation.     

Vulnerability to severe weather and regulation of body mass of Icelandic and British Redshank Tringa totanus

During severe weather, Redshanks suffer the heaviest mortality amongst all the shorebird species wintering around the North Sea coasts of the British Isles. An earlier study had suggested that this resulted from a failure to accumulate sufficient body fat reserves before mid-winter. Detailed field studies in northeast England between 1993 and 1995 of seasonal changes in body mass, and in estimated lean and fat masses, of two races of Redshank, both of which winter in the same estuary, were accompanied by similar studies of small numbers held in captivity with unlimited food. After differences in body size were allowed for, there were no differences in body composition and its seasonal pattern of change in birds of the Icelandic and British races. Body mass changes in wild birds paralleled those in captives between November and March, and mid-winter levels were not limited by food supply; indeed they were slightly higher in a winter with lower prey densities. It is concluded that Redshanks regulate body mass and, indirectly, fat reserves at levels set by a trade-off between the risks of predation and starvation. Unlike most other shorebird species, they take very small prey in relation to their body size and hence must feed for long periods during each tidal cycle to achieve their daily energy intake needs. Thus they have little scope to extend their feeding time during severe weather, which also forces them to feed on ice-free exposed coastal habitats where wind chill cannot be avoided. Both factors lead to more rapid depletion of fat reserves than in other species which have higher energy intake rates or lower total daily requirements.     

Adaptive significance of winter pair bond in male pintail, Anas acuta

To test the female-advantage hypothesis that has been proposed to explain the adaptive significance of winter pair bonds in ducks, we examined the feeding and social behaviors of the northern pintail, Anas acuta. The female-advantage hypothesis assumes that male attendance offers paired females the benefits of increased social status and access to food, as well as less harassment from conspecifics, allowing them to spend more time feeding. Paired females dominated unpaired females, but neither time budgets of feeding nor frequency of feeding was significantly different between unpaired and paired females. The female-advantage hypothesis predicts that paired males spend less time feeding because they must closely guard their partners from harassment by male conspecifics. Paired males defended their mates by chasing and pecking the unpaired males. However, both time budgets of feeding and frequency of feeding were significantly higher in paired males than in unpaired males. Unpaired males frequently approached females while swimming. They performed courtship displays, mostly toward unpaired females. Paired males spent more time feeding by saving time and energy in courtship. We consider that the advantage of winter pairing for males comes from having a mate plus having an increase in feeding frequency. Received: February 20, 2000 / Accepted: May 22, 2000     

Optimal diet selection by white-tailed deer: Balancing reproduction with starvation risk

Summary Energy intake rates of wintering deer vary over time because of variation in the abundance and quality of their natural foods. Accordingly, there is a chance that energy requirements will not be satisfied in a feeding period. This is especially critical because deer are reproductive during winter; hence selecting diets to minimize the risk of starvation may not maximize fitnss. I examined diet selection by white-tailed deer (Odocoileus virginianus) using a risk-sensitive foraging model which predicts the optimal diet when foragers face starvation risks during a reproductive period. Optimal diets were estimated by quantifying the mean and variance in energy intake rate deer could obtain when selecting different potential diets and substituting these values into functions for estimating offspring production and starvation risk. I conducted a field experiment to ask whether deer selected deciduous and coniferous twigs according to model predictions. Starvation risk was manipulated by providing deer supplemental feed. When faced with starvation risks, deer appeared to select diets that balanced offspring production with starvation risk. When starvation risk was climinated, deer tended to select diets that simply maximized their mean energy intake rates.     

Is Foraging Time Limited During Winter? – A Feeding Experiment with Tree Sparrows Under Different Predation Risk

Small passerines are faced with a trade‐off when foraging during winter. Increasing energy reserves makes them more vulnerable to predators, while a low level of reserves exposes them to a high risk of starvation. Whether small birds under these circumstances are allowed to reduce their foraging activity under increased predation risk, for example in feeding sites more exposed to predators, remains controversial in former behavioural and ecological researches. In this study, we investigated the foraging activity of free‐living Tree Sparrow Passer montanus flocks feeding on an artificial feeding platform. The predation risk perceived by the sparrows was manipulated by placing the platform either close to or far from a bushy shelter. Foraging activity, assessed as cumulative activity of sparrows per unit time on the platform, did not differ between the low‐risk and the high‐risk conditions and did not significantly change during the day. Feeding efficiency, assessed as pecking rate, was not either reduced under the high‐risk condition. Our results suggest that sparrows were forced to feed almost continuously during the day in order to maintain their preferred level of energy reserves. However, several behavioural changes helped sparrows to adopt a safer foraging policy when feeding far from cover, as we found in another study. Altogether, sparrow flocks feeding far from cover decreased the overall foraging time (the time when any sparrow stayed on the platform) by approximately 20% as compared to the near cover condition. A possible way to maintain the same level of foraging activity despite of the reduction in overall foraging time is discussed.     

Nutrient constraints in the feeding ecology of an omnivore in a seasonal environment

Summary Nutrient requirements of adult, nonreproductive, omnivorous antelope ground squirrels (Ammospermophilus leucurus) were compared with the nutritional value of their food resources. It was found that nutrient constraints would be important factors in ground squirrel feeding ecology primarily in winter. Potentially important constraints were the requirement for water and nitrogen, and a digestive requirement that average dry matter digestibility of the diet exceed ca. 50%. An unlikely constraint was the requirement for any specific mineral. A linear programming model was used to determine potential diets ground squirrels could consume which satisfied these nutritional requirements and also the ground squirrel's daily energy requirements. During spring ground squirrels could be strict herbivores, but during winter before winter rains ground squirrels had to eat some arthropods to satisfy water requirements.These ground squirrels are not energy maximizers because they spend only one third of their activity period feeding and do not accumulate excess energy as fat. Thus, optimum diets were predicted for winter and spring assuming the goal of feeding time minimization. The model correctly predicted that in wintertime ground squirrels would be primarily granivorous but would consume about 20% arthropods, and that they would switch to herbivory in springtime. Ground squirrels, however, selected a wider dietary range than predicted in both winter and spring. Possible reasons for this discrepancy include an inappropriate assumption that ground squirrels forage for food classes nonsimultaneously, and the possibility that ground squirrels employ sampling as part of their foraging behavior.     

The advantages of social foraging in downy woodpeckers

I investigated the advantages gained by downy woodpeckers (Picoides pubescens) which join mixed-species winter flocks. Woodpeckers foraging alone showed high levels of vigilance as measured by head-cocking rates, and low feeding rates. Woodpeckers foraging with one or two flock members showed intermediate rates of head-cocking and feeding, while woodpeckers foraging with flocks of three or more birds showed low head-cocking rates and high feeding rates. Although local enhancement and copying may contribute to the woodpeckers' increased foraging efficiency in a flock, these do not appear to be the main factors. As downy woodpeckers spend less time on vigilance, they devote more time to foraging, thereby increasing their foraging efficiency     

Cooperative sentinel calling? Foragers gain increased biomass intake

Many foraging animals face a fundamental tradeoff between predation and starvation. In a range of social species, this tradeoff has probably driven the evolution of sentinel behavior, where individuals adopt prominent positions to watch for predators while groupmates forage. Although there has been much debate about whether acting as a sentinel is a selfish or cooperative behavior, far less attention has focused on why sentinels often produce quiet vocalizations (hereafter known as "sentinel calls") to announce their presence. We use observational and experimental data to provide the first evidence that group members gain an increase in foraging success by responding to these vocal cues given by sentinels. Foraging pied babblers (Turdoides bicolor) spread out more, use more exposed patches, look up less often, and spend less time vigilant in response to sentinel calling. Crucially, we demonstrate that these behavioral alterations lead to an increase in biomass intake by foragers, which is likely to enhance survival. We argue that this benefit may be the reason for sentinel calling, making it a truly cooperative behavior.     

The adaptive significance of behavioural ontogeny in some. centrarchid fishes

Synopsis Studies on the ontogeny of behaviour in fish have seldom considered the adaptive significance of the order of appearance of the behaviours. Results of laboratory studies and field observations on the ontogeny of feeding, predator-avoidance, and agonistic behaviour in largemouth bass, Micropterus salmoides, rock bass, Ambloplites rupestris, and pumpkinseed, Lepomis gibbosus, young indicate that the order of appearance of the various behavioural systems enhances the survival of the young. In the laboratory, all species spend significantly more time feeding during the first weeks of free-swimming than the later weeks. During a corresponding period in the field the young are either occupying an offshore area low in predators (rock bass, pumpkinseed) or are being guarded by a parent (largemouth bass); thus the risk of predation is low. When the young are in a predator-rich environment (inshore) both the predator-avoidance response and agonistic behaviour are well developed. Agonistic behaviour is the last to appear and may serve to disperse the young. Dispersal may relate to the feeding mode of the various species and may also reduce the probability of predation. It is apparent that the sequential onsets of the behavioural systems are in concert with ecological events and selective pressures confronting centarchid young.     

Fat reserves and perceived predation risk in the great tit, Parus major

The fat reserves of small birds are built up daily as insurance against starvation. They are believed to reflect a trade-off between the risks of starvation and predation such that in situations of high predation risk birds are expected either to reduce their fat reserves in response to mass-dependent predation risk or to increase them in response to foraging interruptions. We assessed the effect on fat reserves of experimentally altering the perceived (but not the actual) risk of predation of wild great tits at a winter feeding site. The perceived predation risk was alternated between 'safe' and 'risky'. Increasing the perceived risk of predation involved 'swooping' a model sparrowhawk over the feeder at four unpredictable times each day using a remote mechanism We produce evidence that the experiment was suceessfull in altering the perceived risk of predation. As predicted from the hypothesis of mass-dependent predation risk, great tits (Parus major) carried significantly reduced fat reserves during the 'risky' treatment. Furthermore, dominant individuals were able to reduce their reserves more than subordinates. As birds returned to feeders within seconds after a predator 'attack', the reduction in fat reserves cannot be attributed to an interruption in feeding.