Distribution Of Food Resources Research Articles

Living in forest fragments reduces group cohesion in diademed sifakas (Propithecus diadema) in eastern Madagascar by reducing food patch size

Forest fragmentation is thought to threaten primate populations, yet the mechanisms by which this occurs remain largely unknown. However, fragmentation is known to cause dietary shifts in several primate species, and links between food resource distribution and within-group spatial dynamics are well documented. Thus, fragmentation has the potential to indirectly affect spatial dynamics, and these changes may present additional stresses to fragmented populations. I present the results from a 12-month study of Propithecus diadema at Tsinjoarivo, eastern Madagascar, including two groups in fragments and two in continuous forest. Instantaneous data on activity and spatial position were collected during all-day focal animal follows. Fragment groups had much lower cohesion, being more likely to have no neighbor within 5 and 10 m. For continuous forest groups, cohesion was highest in the rainy season (when food patches are large) and lowest in winter (when the animals rely on small-crowned mistletoes), and the chance of having no neighbor within 5 m was positively correlated with mistletoe consumption. Thus their decreased cohesion in fragment groups is inferred to result from their increased reliance on mistletoes and other small resources, which causes them to spread out among multiple patches. This scenario is consistent with the reduced body mass of subordinate individuals (males and immatures) in fragments, and suggests the occurrence of steeper within-group fitness gradients. Further research is necessary to determine whether these patterns apply to other primates; however, since fragmentation tends to cause the loss of the largest trees, many primates in fragments may lose their largest food resources and undergo similar behavioral shifts.

The effect of the spatial distribution of winter seed food resources on their use by farmland birds

Summary Agri‐environment measures providing winter seed are central to current management activities aiming to reverse granivorous farmland bird declines. Previous research has considered the effectiveness of particular agri‐environment options, but the influence of their distribution in the landscape, an important factor in determining cost‐effectiveness, has received less attention. We used a large‐scale field experiment in eastern England, featuring 10 replicates of a spatial arrangement of seven artificial feeding stations separated by different distances, to investigate bird movements between discrete winter food resources. Feeding sites were established and bird use monitored at least weekly over two winters (November–March). Habitat type in the areas surrounding the feeding sites was also recorded. Two measures of feeding site use were analysed as functions of the distance from the nearest alternative feeding site, controlling for ambient resource availability, for 11 passerines (including chaffinch Fringilla coelebs, reed bunting Emberiza schoeniclus and yellowhammer Emberiza citrinella and non‐granivores such as blue tit Parus caeruleus). Feeding site use varied significantly with separation distance for nine species. For most, both maximum counts and bird minutes were higher at more isolated sites, but the opposite was true for yellowhammer and reed bunting. Most relationships incorporated significant thresholds at separations of around 500 m, with low site use below the threshold and high above it (or vice versa). The results suggested that species such as chaffinch and blue tit made disproportionately more use of food at isolated sites than at clumped ones, but that reed buntings and yellowhammers used food in proportion to its availability, moving freely between more clumped patches. In both cases, birds tended to share resources separated by 500 m or less. At greater separations, resources tended to be used by discrete groups of birds. Radio‐tracking and colour‐ringing work produced corroborative evidence. Synthesis and applications. The response of birds to the experimental food resource distribution implies that creating resource patches more than 1 km apart should be most cost‐effective, a recommendation that can inform agri‐environment scheme planning directly. This distance may represent a minimum, however, because birds might locate standing crops more readily than inconspicuous artificial food patches.

A framework for predicting and visualizing the East African wildebeest migration‐route patterns in variable climatic conditions using geographic information system and remote sensing

AbstractIn the Serengeti–Mara ecosystem of East Africa, the migrating wildebeests’ (Connochaetes taurinus) response to food resource distribution and terrain complexity impacts their movement characteristics. This manifests in varying ways such as movement speed, direction, turning frequency, and moving distance. To investigate these characteristics, indices derived from vegetation quantity (normalized difference vegetation index, NDVI) and relief (slope) were used in our previous work to quantify the relationships between migration route location versus vegetation, relief complexity, and their combination. Least cost pathways determined using these indices were representative of approximate migration routes. The simulated routes were shown to be strongly influenced by vegetation during the dry season. However the impact of climatic change (rainfall) on route location was not investigated though known to influence vegetation recovery patterns. This paper specifically addresses the impact of climatic change on route location. The mean monthly rainfall data were used to classify the rainy and dry seasons in the Serengeti, the Western, and the Mara areas as normal, drier, or wetter than normal, over the 1986–1997 period. The classification is based on the mean monthly rainfall variability about the 11‐year seasonal mean. Regression analysis showed strong linear relationships between rainfall and mean NDVI for each one of the three areas. The subsequent seasonal classification based on the corresponding habitat vegetation characteristics (NDVI) revealed the relative variation of vegetation with rainfall. Using the derived general categories, migration routes are then predicted for the various categories using a “route attractivity index.” The seasonal migration routes were shown to change depending on the relative abundance of the rainfall during the dry season. Dry season migration routes tended toward areas with better vegetation activity, i.e., those characterized by higher NDVI gradients. Our results showed that during the western trek, wetter dry seasons have the effect of delaying the herds movement northwestward. During the northern trek, wetter dry seasons have the effect of delaying the tendency to move westward. However the variation in rainfall conditions during the rainy and dry season had no significant influence on the southern trek route location. We assume that predicted routes based on average general category conditions for different years are representative of main migration route patterns for similar seasons, therefore they are well suited for approximate route prediction, if the climatic characteristics of the year are known.

Unequal division of food resources suggests feeding hierarchy of signal crayfish ( Pacifastacus leniusculus) juveniles

Individual food intake of two-year-old signal crayfish ( Pacifastacus leniusculus Dana) juveniles (initial carapace length 22.81 ± 1.68 mm and wet weight 3.08 ± 0.67 g) fed semi-moist gelatine-based food were measured four times (days 28, 43, 64 and 91) during a three-month experimental period. Food intake competition results between juveniles from three separate groups was evaluated with the help of feeding ranks that were assessed on the basis of the individual mean values of consumption data from repeated radiography measurements. Signal crayfish juveniles showed high variability in food intake both among juveniles in a group (inter-individual) and within individuals day-to-day variation (intra-individual). This unequal distribution of food resources and its relation to animal size as a main factor to control food intake suggested feeding hierarchy among crayfish juveniles reared communally. This is supported by observed low day-to-day variations in food intake among juveniles with high consumption. The relationship between competition success and size-based dominance were analysed with the change of individual carapace length rank during the experiment based on growth and food consumption data. It seemed that signal crayfish juveniles can raise their rank either by consuming high amounts of food or being very efficient.

Distance influences the foraging decisions of emperor and saddleback tamarins

AbstractStudies on great apes, Old World monkeys, and New World monkeys suggest that anthropoid primates may retain a detailed spatial representation of the distribution of important food resources in their home range. This is evidenced by selecting the shortest travel routes between sets of feeding sites. In this research, I tested whether distance influences between‐patch foraging decisions of free‐ranging social groups of black‐chinned emperor tamarins Saguinus imperator imperator and Weddell's saddleback tamarins Saguinus fuscicollis weddelli living in a 100‐ha forest reserve (Zoobotanical Park of the Universidade Federal do Acre) located in Rio Branco, State of Acre, Brazil. Four artificial feeding sites (feeding stations) were established within the home ranges of one group of each species. They were distributed in a diamond configuration and located from 58 to 256 m from each other. Each feeding station was composed of eight feeding platforms (two of which baited with one banana). Data collection was conducted from 3 October to 28 November 1997 (54 days). To determine whether distance among feeding sites influences tamarin daily between‐patch foraging decisions, it was recorded whether a group visited the nearest, intermediate or farthest station after departing from a particular one. The emperor tamarin group visited the feeding stations 207 times (average=3.8 visits day−1) and the saddleback tamarin group visited the feeding stations 265 times (average=4.9 visits day−1). After arriving at a feeding station, both species tended to choose the nearest station to visit and to avoid the farthest one at a frequency greater than chance, supporting the contention that these tamarins know the distribution and spatial relationships of their main food resources.

Habitat selection by nocturnal passerine migrants en route: mechanisms and results

Habitat use and habitat selection are essential for successful stopovers. Passerine migrants use habitats in a clearly non-random manner, even if many species utilise a broader range of habitats during passage than during breeding or wintering. Habitat selection proceeds as a sequence of events: landfall; search/settling, including redistribution across habitats if necessary; and habitat exploitation, with all stages probably condition-dependent. This review is aimed at studying this sequence and also the factors which govern decision-making in nocturnal passerine migrants at all levels. In most cases, habitats are (pre)selected by migrants already at landfall using both visual and acoustic cues. After landfall, migrants start to perform direct sampling of habitats during which they may move constantly and perform fine-tuning of their habitat choice. Some species subsequently occupy a small home range in a particular (micro)habitats, whereas others continue to move broadly during the whole stopover period. An interaction of several factors shapes the use of habitats after landing, among which are migrants’ innate preferences and functional morphology, foraging strategies and food resource distribution, habitat carrying capacity and exposure to predators. The large-scale spatial context probably also plays a role which might be currently underestimated.

Resource distribution mediates synchronization of physiological rhythms in locust groups

Synchronized behaviour is common in animal groups. In ant colonies, synchronization occurs because active ants stimulate their neighbours to activity. We use oscillator theory to explain how stimulation from active neighbours synchronizes activity in groups of solitarious locusts via entrainment of internal physiological rhythms. We also show that the spatial distribution of food resources controls coupling between individual locusts and the emergence of synchronized activity. In locusts (Schistocerca gregaria), individual schedules of activity and quiescence arise from an irregular physiological oscillation in feeding excitation (i.e. hunger). We show that contact with an active neighbour increases the probability that a locust becomes active. This entrained activity decreases the time until the locust feeds, shifting the phase of its hunger oscillation. The locusts' internal physiological rhythms are thus brought into alignment and their activity becomes synchronized. When food resources are clumped, contact with active locusts increases, and this increase in the strength of coupling between individuals leads to greater synchronization of behaviour. Activity synchronization might have functional significance in inhibiting swarming when resources are dispersed and accelerating it in more favourable clumped environments.

A temporal analysis of the foraging flights of feral pigeons (Columba livia f. domestica) from three Italian cities

Foraging flights of feral pigeon populations may differ in occurrence and extent from town to town. In this paper, the annual pattern of such flights from three medium‐sized Italian cities (Venice, Parma and Lucca) is described and compared with that recorded for a Mediterranean population of wild rock doves from Sardinia. The data provide evidence of the similarity of these flights both within urban populations and between feral pigeons and wild rock doves. On the other hand, the presented results point to a noticeable flexibility of this behaviour, whose features seem finely adapted to the environmental features of an urban habitat and its surroundings. In particular, the distribution of food resources and of the annual trend of reproductive attempts appear to exert a leading role in shaping the characteristics of these flights.

Captive female gorilla agonistic relationships with clumped defendable food resources

Minimal feeding competition among female mountain gorillas (Gorilla gorilla beringei) has resulted in egalitarian social relationships with poorly defined agonistic dominance hierarchies. Thus, gorillas are generally viewed as non-competitive egalitarian folivores that have had little need to develop effective competitive strategies to access food resources. However, this generalization is inconsistent with more recent research indicating that most gorillas are frugivorous, feeding on patchily distributed food resources. The current study at Howletts Wild Animal Park, Kent, England, explores the effects of clumped and defendable foods on female gorilla agonistic relationships among three groups of western lowland gorillas (G. g. gorilla), conditions that are predicted to lead to well-differentiated agonistic dominance hierarchies among female primates. The Howletts gorillas foraged all day on low-energy/-nutrient, high-fiber foods widely distributed around their enclosure by the keepers. However, they also had periodic access to high-energy foods (e.g., nuts, raisins, strawberries, etc.) that the keepers would spread in a clumped and defendable patch. Frequencies of agonistic and submissive behaviors between females and proximity data were gathered. High-status females were found to monopolize the food patch and kept the low-status females at bay with cough-grunt threat vocalizations or by chasing them away. Agonistic interactions were initiated mostly by females of high status; these were directed towards females of low status and were generally not reciprocal. In addition, females of low status engaged in submissive behaviors the most often, which they directed primarily at females of high status, especially in response to aggression by the latter. Agonistic interactions between high- and low-status females had decided outcomes more often than not, with low-status females the losers. Competition over highly desirable foods distributed in defendable clumps at Howletts appears to have led to well-defined dominance relationships among these female gorillas.

Application of GIS to investigate the use of space in coral reef fish: a comparison of territorial behaviour in two Red Sea butterflyfishes

The space use of two coral‐feeding Red Sea butterflyfish species (Chaetodon austriacus and C. trifascialis) was studied at three sites in the Gulf of Aqaba to determine the extent of intraspecific territoriality. Individuals or pairs were observed in shallow water (<5 m). Their locations were recorded on maps of each study reef. The Animal Movement Analysis Extension (AMAE) in ArcView was used to plot territory borders and compute territory size for each species. Chaetodon austriacus, a generalist corallivore that exploited evenly distributed food resources, maintained small exclusive pair territories with clearly defined territory boundaries. In contrast, C. trifascialis, a specialist corallivore that exploited patchily distributed food resources, demonstrated considerable variation in territorial behaviour that ranged from the defence of small exclusive solitary territories to the shared use of a large home range. Comparisons of territory area estimates showed that 95% kernel probability density function territory boundaries matched intuitive territory boundaries and, unlike the minimum convex polygon area, did not contain obvious areas that were not used by individuals or pairs. We show that comparing different territory size measures can be very useful in describing subtle differences in territorial behaviour between species and studies. For this purpose, GIS is an ideal technology with which to carry out such analyses quickly and easily.

RESOURCE AND SPATIAL-USE PATTERNS OF AN ENDANGERED VERTEBRATE POLLINATOR, THE LESSER LONG-NOSED BAT

Understanding how the distribution and abundance of food resources influence space use of organisms is an important element of successful conservation and recovery strategies for endangered species. We investigated interrelationships between space use, activity patterns, and food resources for lesser long-nosed bats (Leptonycteris curasoae), an endangered nectar-feeding bat, during an energetically demanding phase of its annual life cycle. We estimated the size of home ranges (95% kernel areas) and core use-areas (50% kernel areas) of bats and estimated density of their forage plant (Agave palmeri) in and near these use areas. Density (x̄± SE plants/ha) of flowering agaves within home ranges (3.6 ± 1.04) exceeded that which was available on the landscape (1.8 ± 0.36), indicating that bats selected areas with high food abundance. Although density of agaves within home ranges of bats differed in successive years (1998: 3.6 ± 1.04; 1999: 0.8 ± 0.15), sizes of home ranges and core use-areas of adult bats were similar between years, suggesting that the relationship between home-range size and density of food resources was mediated by other factors. Differences in activity budgets of bats between years suggest that bats altered their behavior in response to changes in food abundance, allocating more time to foraging the year fewer flowering plants were present. Consequently, reductions in agave density could increase energy demands of foraging bats and reduce the chances of successful recovery of lesser long-nosed bat populations.

Food Shortage Disrupts Social Organization: The Case of Red Squirrels in Conifer Forests

A recent conceptual model of spatial organization in vertebrates, based upon changes in home range overlap with habitat quality, ‘the space-use model’, predicts large and strongly overlapping home ranges and absence of territorial behaviour in habitats with poor food availability. We investigated whether the model can be extended to predict intra-population variation in space-use in a habitat with strong temporal variation in resource abundance. We studied space use of Eurasian red squirrels (Sciurus vulgaris) in subalpine conifer forests over 4 years with strong fluctuations in seed production. Norway spruce dominated forests are resource limited habitats for squirrels, and tree seed availability is gradually depleted in the year following a poor seed-crop. Male and female squirrels responded to spruce seed-crop failure in 2000 by strongly increasing their home ranges and core-areas in the following year (mean MCP ± SE in summer and autumn, respectively: 2001, 122.9±14.1 ha and 84.3±9.4 ha, against 43.0±6.4 ha and 20.8±3.8 ha in 2002, and 22.7±1.5 ha and 21.4±2.0 ha in 2003). In 2001, half of the animals, those with the poorest quality pre-dispersal home ranges, emigrated to areas with more larch. Residents had multi-nuclear core-areas. Also, intra-sexual core-area overlap (males by males, females by females) was higher in 2001 and summer 2002, than in autumn 2002 and in 2003 (means ± SE in summer and autumn, respectively: males by males, 2001, 52±8 and 44±7%, 2002, 80±30 and 15±11%, 2003, 37±19 and 26±14%; females by females 2001, 52±10 and 112±32%, 2002, 55±27 and 0±0%, 2003, 12±8 and 0.1±0%). Red squirrels responded to food shortage by moving to patches with other food resources and abandoned the spacing pattern of reduced core-area overlap among males and nearly exclusive core-areas among females, found in less variable habitats. After richer seed-crops in 2001 and 2002, it took squirrels about a year to reduce the size of their home ranges and core-areas and return to a spacing pattern of stable home ranges and intra-sexual territoriality of adult females. These results are consistent with the space-use model and show that spacing behaviour in red squirrels is a plastic, conditional strategy with individuals adapting the size and/or location of their home ranges in relation to local distribution and abundance of food resources.

Population Genetics of Wood-Feeding Cockroaches in the Genus Cryptocercus

Members of the genus Cryptocercus are xylophagous, wingless, subsocial cockroaches that inhabit decaying logs in temperate forests. Given their winglessness, subsocial living, and the patchy distribution of food resources (decomposing logs), it is likely that Cryptocercus populations are substructured. Allozyme variation at eight polymorphic loci was assayed for 10 subpopulations of Cryptocercus darwini and 13 subpopulations of Cryptocercus wrighti, both of which are distributed in the Appalachian Mountains. The mean F(IS) was 0.13 and F(ST) was about 0.25 for both C. darwini and C. wrighti. The relatedness among individuals of a subpopulation of both species was not significantly different from that expected among full sibs. In terms of how genetic variation is partitioned, C. darwini and C. wrighti differed from each other substantially. Most of the genetic variation occurred among subpopulations of C. wrighti in the same region and among subpopulations of C. darwini in different regions. We discuss the factors that may have contributed to the observed similarities and differences in the breeding structure of the two species.

Landscape scale, heterogeneity, and the viability of Serengeti grazers

AbstractSpecies persistence can be threatened by substantial temporal variation in food resources over time. On the other hand, spatial heterogeneity in resources at the landscape scale might allow mobile consumers to compensate for temporal variability in resource availability at the local scale. We evaluated this hypothesis, using an extensive data set on foraging, grass growth, and movement by Thomson's gazelles living on the Serengeti Plains. Here we show that modelled populations of Thomson's gazelles can only persist under Serengeti conditions in the face of observed levels of rainfall stochasticity by making adaptive movements to take advantage of ephemeral spatial distributions of food resources. More importantly, our models suggest that Thomson's gazelles in Serengeti require unrestricted access to relatively large areas of grassland (&gt; 1600 km2) to guarantee long‐term persistence, particularly when there is positive spatial autocorrelation in resource abundance, as is the case in Serengeti. If this proves to be true for other species and/or other systems, then understanding of complex behavioural responses to spatially and temporally heterogeneous food supplies may be essential to successful conservation of grazing herbivores.

Excluding neighbours from territories: effects of habitat structure and resource distribution

Small animals vulnerable to predation, such as rodents, have a strong preference for sites that provide physical protection from predators. This is likely to affect not only their use of space and activity but also the ease with which they can defend a territory, since the likelihood of encountering (or losing) intruders and their willingness to compete are affected by the quality and distribution of resources and the structural complexity of the habitat. To examine how these different habitat factors interact to influence territorial behaviour in male house mice, Mus domesticus, which inhabit environments with very different levels of complexity and resource distribution, we housed male–female pairs in enclosures representing one of eight habitat types varying in ground-level structure (open/complex), overhead cover (present/absent) and distribution of protected nest sites and food (resources clumped together/scattered). Neighbouring pairs were allowed to interact five times over 3 days and we examined behaviour during the first (unfamiliar) and fifth (familiar) periods. Initially, encounter rates were two to three times higher in open habitats with overhead cover than in either complex habitats or open habitats without cover, and higher when resources were scattered than when they were clumped. Aggressive interactions between unfamiliar males were more prolonged in habitats with open ground-level structure, where pursuits followed restricted pathways. The effects of overhead cover on aggression among unfamiliar neighbours unexpectedly depended on the origin of the mice. Once neighbours learnt the outcome of their interactions, aggressive interactions were most prolonged in habitats with scattered resources and complex ground-level structure, making these habitats the most difficult to defend.

SPACING AS A PREDICTOR OF SOCIAL ORGANIZATION IN KANGAROO RATS (DIPODOMYS HEERMANNI ARENAE)

We examined intraspecific space use of free-ranging kangaroo rats (Dipodomys heermanni) during the breeding season using behavioral observations and radiotelemetry. Home ranges of males were significantly larger than those of females. Female D. heermanni maintained exclusive territories with essentially nonoverlapping home ranges, whereas home ranges of males overlapped with both same- and opposite-sex conspecifics, reflecting the different strategies of the different sexes. This follows a general pattern found in mammals in which spacing reflects limiting resources. There was, however, high individual variation in home range size for males, which may suggest a role for social interactions in determining spatial behavior in this species. D. heermanni, a medium-size species, appears intermediate in space use compared with the larger D. spectabilis and the smaller D. merriami. Spacing systems characterize the pattern of distribution of individuals in a population in space and time. The location of an individual is influenced by presence or absence of other individuals (Brown and Orians 1970), distribution of food resources (Covich 1976; Emlen and Oring 1977), and extent of suitable habitat. The social processes by which resources are allocated among members of the population determine spatial organization. Hence, spatial organization of a population can be used to predict its social organization. Patterns of space use by mammals have been the subject of numerous discussions and empirical tests (Lott 1991). One metric for space use is home range size, which is a compromise between environmental conditions and selective factors such as primary production, individual metabolic requirements, predation, and social pressures. These interacting factors often lead to different levels of social interaction between and within species. For solitary rodents in particular, variation in use of space is related to sex, season, geography, and competitive behavior (Armitage 1999; Ebensperger and Bozinovic 2000;

SOCIAL SYSTEM AND SPATIAL ORGANIZATION OF WILD GUINEA PIGS (CAVIA APEREA) IN A NATURAL POPULATION

This study aims to elucidate the social system of the wild cavy (Cavia aperea), the feral ancestor of the domestic guinea pig, whose behavior under natural conditions is almost unstudied. Therefore, a population of C. aperea was investigated for a 6-month period in its natural habitat in southeastern Brazil. The animals’ space use was examined via radiotelemetry, social interactions were recorded using direct observations, and genetic relationships were analyzed via DNA fingerprinting. Additionally, the distribution of plant cover, food resources, and predation risk was recorded to investigate the impact of different ecological factors on evolution of the social system. In the study period, a low population density was detected and a strong predation pressure existed, which resulted in a high mortality rate of C. aperea. Spatial distribution of wild cavies was strongly associated with areas of dense ground vegetation. Within these areas, small groups consisting of 1 male and 1–2 females occupied stable home ranges that overlapped only slightly with home ranges of adjacent groups. Social interactions were restricted mainly to individuals of the same group, and initial analyses of paternity indicate that the females’ offspring were sired by the respective group male. The social system and spatial organization of C. aperea are regarded as adaptations to high predation pressure because in dense vegetation small group size reduces the risk of detection by predators. Moreover, habitat use, social interactions, and paternity point to a single-male system in this low-density population of wild cavies.

Influences of Anthropogenic Resources on Raccoon (Procyon lotor) Movements and Spatial Distribution

Abundance and distribution of food resources can profoundly affect movements and spatial distribution of solitary carnivores. Food availability and distribution are often altered in urbanized systems due to occurrence of abundant and highly concentrated anthropogenic resources. To address effects of these resources on movements and spatial distribution of raccoons (Procyon lotor), we simultaneously studied populations inhabiting urban (Ned Brown Forest Preserve), suburban (Max McGraw Wildlife Foundation), and rural (Glacial Park) open areas in northeastern Illinois. Estimates of sizes of home ranges were smaller for urban (range, 25.2–52.8 ha, n = 29) and suburban (21.4–37.2 ha, n = 34) than rural (71.2–182.4 ha, n = 39) raccoons during all seasons (P < 0.05). Seasonal changes in sizes of home ranges were least pronounced at the suburban site. Seasonal shifts in activity centers also were small for raccoons at the suburban site and for most raccoons at the urban site. Spatial distribution was aggregated during all seasons at the urban site, and during all seasons except summer 1997 at the suburban site. Abundant and relatively stable artificial resources typical of urbanized systems contributed to reduced size and increased stability of home ranges. Further, concentration of these resources into rich and separated patches resulted in an aggregated distribution. Similar responses to abundant and concentrated resources have been documented for solitary carnivores in other, more natural, systems.

INFLUENCES OF ANTHROPOGENIC RESOURCES ON RACCOON (PROCYON LOTOR) MOVEMENTS AND SPATIAL DISTRIBUTION

Abundance and distribution of food resources can profoundly affect movements and spatial distribution of solitary carnivores. Food availability and distribution are often altered in urbanized systems due to occurrence of abundant and highly concentrated anthropogenic resources. To address effects of these resources on movements and spatial distribution of raccoons (Procyon lotor), we simultaneously studied populations inhabiting urban (Ned Brown Forest Preserve), suburban (Max McGraw Wildlife Foundation), and rural (Glacial Park) open areas in northeastern Illinois. Estimates of sizes of home ranges were smaller for urban (range, 25.2–52.8 ha, n ¼ 29) and suburban (21.4–37.2 ha, n ¼ 34) than rural (71.2–182.4 ha, n ¼ 39) raccoons during all seasons (P , 0.05). Seasonal changes in sizes of home ranges were least pronounced at the suburban site. Seasonal shifts in activity centers also were small for raccoons at the suburban site and for most raccoons at the urban site. Spatial distribution was aggregated during all seasons at the urban site, and during all seasons except summer 1997 at the suburban site. Abundant and relatively stable artificial resources typical of urbanized systems contributed to reduced size and increased stability of home ranges. Further, concentration of these resources into rich and separated patches resulted in an aggregated distribution. Similar responses to abundant and concentrated resources have been documented for solitary carnivores in other, more natural, systems.

At-sea distribution of female southern elephant seals relative to variation in ocean surface properties

AbstractWe examined the relationships between physical oceanography (sea surface temperature – SST, sea surface height anomaly – SSH, ocean colour – OC, bathymetry – BA, sea-ice concentration – SI, and their associated gradients) and the foraging distribution (time at sea) of female southern elephant seals using generalized linear and generalized additive models (GLM and GAM). Using data from 28 separate foraging trips (22 unique individuals) over two years, we found that during the post-lactation trips (summer), the best GLM demonstrated a negative relationship between time at sea and SST and BA, but a positive relationship with SST gradient and SSH. During the post-moult (winter) trips, there was a negative relationship with OC gradient, SSH, and BA. The best post-lactation GAM identified a positive relationship with OC gradient, negative relationships with OC and SST gradient, and a non-linear relationship with SST. For the post-moult trip there was a negative relationship with OC, SST, BA and BA gradient, and a positive relationship with SST gradient. The relationship between the predicted time and observed time at sea was significant only for the post-lactation GAM, although predictability was low. That SST and its gradient predicted a small, but significant proportion of the variation in time at sea is indicative of the frontal zones within this area that are generally more biologically productive than surrounding regions. It appears that coarse-scale oceanographic configuration influences foraging behaviour in southern elephant seals only subtly. Nonetheless, some of the mechanisms influencing predator foraging are congruent with expectations of distribution of marine food resources at coarse spatial scales.