Socioecological correlates of inter-individual variation in orangutan diets at Ketambe, Sumatra

The diet of great apes consists of several hundred plant species. The factors determining diet differences have been examined between populations but not within a population, probably due to the confounding effect of seasonal fluctuations on fruit availability. In Sumatran orangutans (Pongo abelii), fruit availability appears to be sufficiently high year round to have little influence on diet composition, which in turn allows for addressing this question. We examined the diet of eight adult female orangutans at Ketambe, Sumatra, and investigated whether fig and non-fig fruit availability, association time, and/or home range measures influenced dietary overlap between female dyads. Between most pairs, females’ diets were different: 16 out of 23 pairs had a significantly low diet species overlap. Only fig diet overlap was influenced (negatively) by the availability of non-fig fruit. Association time only influenced (positively) fig diet overlap. Hence, orangutans gathered in fig trees when non-fig fruit availability was low. Home range measures did not influence overall diet overlap. To our knowledge, this is the first study showing that, while controlling for confounding factors, individuals with similar energetic requirements, from the same population and sharing the same area, make different dietary choices relatively to their preferred (non-fig) fruit constituting the majority of their diet. Social transmission, with putative matrilineal diet traditions, suitably explains these results. We discuss the implications of the findings for orangutan conservation, namely on reintroduction and the felling of fig trees.     

Determinants of male spacing behavior in microtines: an experimental manipulation of female spatial distribution and density

Theory on microtine mating systems predicts that male spacing behavior will be related to female spatial and temporal distribution. However, data from a natural population of field voles, Microtus agrestis, indicated a potential influence of female density on the spacing behavior of males. Therefore, I experimentally investigated the relative importance of female density and female spatial distribution for the spacing behavior of males in M. agrestis. Males were radio-tracked in enclosed natural habitats in which females at different densities were placed in two different spatial arrangements: clumped versus even distribution. Female density was the main factor determining male spacing behavior. At the high female density males had smaller home ranges and moved shorter distances between radio-tracking recordings. Also, home ranges were more exclusive at high female density. However, since there was a significant positive correlation between home range size and range overlap, range exclusiveness seemed to be influenced by female density indirectly through the effect of range size. Female spatial distribution, on the other hand, had no influence on male home range exclusiveness.     

Comparison of methods for determining key marine areas from tracking data

There is an urgent need to identify key marine areas for conservation, particularly in the high seas. A range of techniques have been applied to tracking data from higher predators, particularly seabirds and pinnipeds, to determine the areas of greatest use. This study compared three commonly used methods—kernel, first-passage time and state-space modelling—and a new approach, minimum displacement rate, for the analysis of data from the wandering albatross Diomedea exulans of Bird Island, South Georgia, tracked during the chick-rearing period. Applied to a single track, these four models identified similar marine areas as important. The greatest similarity in areas identified occurred when model assumptions were shared (such as slow speed indicating spatial preference) even when methods modelled these assumptions differently (e.g. Bayesian inference versus cumulative density surface). A gridded overlap approach applied to all tracks revealed core areas not apparent from results of any single analysis. The gridded approach also revealed spatial overlap between methods based on different assumptions (e.g. minimum displacement rate and kernel analysis) and between individuals. Although areas identified as important by kernel and first-passage time analysis of a single track were biased towards resting locations during darkness, this does not negate the requirement for their protection. Using the gridded overlap approach, two distinct core regions were identified for the wandering albatross; one close to the breeding colony and another 800 km to the North–West in the high seas. This convenient and pragmatic approach could be applied to large data sets and across species for the identification of a network of candidate marine protected areas in coastal and pelagic waters.     

Ecology of Conus on eastern Indian Ocean fringing reefs: Diversity of species and resource utilization

The most diverse assemblages of the genus Conus known occur on fringing coral reefs in Thailand and Indonesia. As many as 27 congeneric species of these gastropods inhabit a single reef; in all, we examined 1,350 individuals of 48 species. Several attributes of the populations we observed conform to expectations of a model of ecological characteristics of bench and reef Conus proposed by Kohn (1971a). Number of species (S) averaged 15, and species diversity (H″) averaged 2.3 in the most heterogeneous habitat type — topographically complex, subtidal reef platforms (Type III habitat). Both species richness and evenness of distribution of individuals among species contribute strongly to H″. Fewer congeners and greater numerical dominance by single species characterize more homogeneous habitats. On subtidal reef platforms with large areas of sand substrate and less coral limestone (Type I–III habitat), mean values were S=10, and H″=1.6. In the one intensively studied, truncated reef-limestone platform (Type II–III intermediate habitat), S=13 and H″=1.4. Summed population density of all Conus species in Type III and I–III habitats is similar (0.02 to 0.05 individuals /m²) and comparable to estimates from similar habitats elsewhere in the Indo-West Pacific region. Mean density (0.7/m²) and other population attributes in Type II–III habitat more closely resemble those of Type II than Type III habitats in general. We combined analysis of species diversity and other attributes of assemblages in habitats of different environmental complexity with analysis of microhabitat and food-resource utilization, in order to demonstrate the extent to which specialization on different resources occurs in assemblages differing in diversity and habitat type. In the habitats studied, co-occurring species of Conus specialized to a greater extent on different prey species than on different microhabitat patches, but degree of microhabitat specialization was greater than in similarly complex habitats with assemblages of lower diversity elsewhere in the Indo-West Pacific region. While most Conus species preyed primarily on a different species or higher taxon of polychaetes, diets are not more specialized or dissimilar than in similar habitats elsewhere. Degree of specialization on different prey is not correlated with Conus species diversity in the different types of habitats studied. The data lead to the conclusion that differential predation is as important — and differential microhabitat utilization is more important — in permitting coexistence of potentially competing congeners, compared with conditions in habitats of comparable heterogeneity that support fewer congeners farther from the center of the Indo-West Pacific region. Pairwise comparisons of congeners indicate that many species pairs have low or no overlap in both microhabitat and food utilization. Members of species pairs with high overlap in microhabitat utilization typically eat different prey organisms, and those with similar diets typically occupy different habitats or microhabitats. This applies to molluscivorous as well as vermivorous species. Information on the diets of 11 species is reported here for the first time. Of 48 Indo-West Pacific Conus species whose food is now known, 35 prey on polychaetes, 2 on enteropneusts, 6 on gastropods, and 5 on fishes. Vermivorous Conus prey on relatively few of the polychaete species present in the environments. Species eaten represent only 12% of a total estimated polychaete population density of 27,000 individuals /m². Certain very abundant polychaetes may be protected from predation by Conus by their small size, others by their long tubes. Two new aspects of size-selective predation by Conus are reported: (1) Although comparisons of predation rate with prey standing-crop suggest that food is plentiful, selective predation on the largest prey individuals present suggests that only small proportions of prey-species populations may have large enough body size to repay foraging effort by the Conus present; (2) composition of the diet changes qualitatively with increase in body size in several vermivorous Conus species; shifting by larger individuals to larger prey species could be documented in C. ebraeus.     

Life history and population dynamics ofKinbergonuphis simoni (Polychaeta: Onuphidae)

The relationship between life-history characteristics and population dynamics were investigated in the onuphid polychaeteKinbergonuphis simoni (Santos, Day and Rice) between 1982 and 1987. The studied population is located in Upper Tampa Bay, Florida, USA. This worm attains sexual maturity at 5 to 10 mo of age, depending on temperature. Several consecutive broods are produced during a female's life time, with 7 to 26 young per brood. Adults die in June–July after the breeding season. Generations of breeding individuals do not overlap and the replacement of generations occurs in July–August. Only one extended breeding season is experienced per life time. Life span does not exceed 2 yr. Field population density in 1982 was high in fall and spring (2000 to 9000 individuals/m²), low in summer (1600 individuals/m²), and slightly depressed in winter (2500 to 4000 individuals/m²). Changes in population density may be explained by seasonal, temperature-controlled changes in instantaneous birth and death rates. Birth rates are high in fall and spring, while death rates are high in early summer. Death of juveniles contributes to the winter density decrease.     

Ranging patterns of bottlenose dolphins living in oceanic waters: implications for population structure

Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based surveys conducted over a 6-year period in an area of approximately 5,400 km² (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation within the population of the Azores.     

Ranging patterns of bottlenose dolphins living in oceanic waters: implications for population structure

Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based surveys conducted over a 6-year period in an area of approximately 5,400 km² (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation within the population of the Azores.     

Relationships between spacing behavior and growth rates: A field study of lizard feeding territories

Summary Relationships between spacing behavior and growth rates were investigated in a field experiment with juvenile lizards, Anolis aeneus. The behavioral variable most closely related to juvenile growth was distance moved per unit time. This variable had a curvilinear relationship with growth, such that juveniles moving approximately 400 cm/h grew more rapidly than those traveling either larger or shorter distances per unit time. Daily fluctuations in arthropod abundance were also related to growth rates, with restricted growth during periods of low food availability. Temporal fluctuations in prey and distance traveled per unit time had independent effects on growth; together these two variables accounted for 43% of the variance in growth rate for the juveniles in this study.Territory size, overlap and social status appeared to affect growth indirectly, by influencing distance traveled per unit time. Optimal travel distances of around 400 cm/h were most likely when a juvenile had a relatively exclusive territory of about 0.5 m². High ranking juveniles were more apt to achieve this spacing pattern than were low ranking juveniles, but some high ranking juveniles had very large territories, extensive overlap with subordinates, supraoptimal travel distances and relatively low growth rates. Low ranking juveniles tended to fall into two groups: subordinates, with a small home range overlapping that of a more dominant individual and low travel distances, and floaters, with a large home range overlapping several more dominant individuals and high travel distances. Although a few low ranking juveniles achieved travel distances permitting high growth rates, most had either supra or suboptimal travel distances and relatively low growth rates.     

Lifetime reproductive success and composition of the home range in a large herbivore

The relationship between individual performance and nonrandom use of habitat is fundamental to ecology; however, empirical tests of this relationship remain limited, especially for higher orders of selection like that of the home range. We quantified the association between lifetime reproductive success (LRS) and variables describing lifetime home ranges during the period of maternal care (spring to autumn) for 77 female roe deer (Capreolus capreolus) at Trois-Fontaines, Champagne-Ardenne, France (1976-2000). We maintained population growth rate (adjusted to account for removals of non-focal animals) near rmax, which enabled us to define the fitness-habitat relationship in the absence of density effects. Using a negative binomial model, we showed that a roe deer's incorporation into its home range of habitat components important to food, cover, and edge (meadows, thickets, and increased density of road allowances) was significantly related to LRS. Further, LRS decreased with increasing age of naturally reclaimed meadows at the time of a deer's birth, which may have reflected a cohort effect related to, but not entirely explained by, a decline in quality of meadows through time. Predictive capacity of the selected model, estimated as the median correlation (rs) between predicted and observed LRS among deer of cross-validation samples, was 0.55. The strength of this relationship suggests that processes like selection of the site of a home range during dispersal may play a more important role in determining fitness of individuals than previously thought. Individual fitness of highly sedentary income breeders with high reproductive output such as roe deer should be more dependent on home range quality during the period of maternal care compared to capital breeders with low reproductive output. Identification of the most important habitat attributes to survival and reproduction at low density (low levels of intraspecific competition) may prove useful for defining habitat value ("intrinsic habitat value").     

Genetic relatedness and space use in a behaviorally flexible species of marmot, the woodchuck (Marmota monax)

Solitary species show several patterns of space use and relatedness. Individuals may associate randomly or may live near female or male kin, often as a result of natal philopatry or dispersal patterns. Although usually described as solitary or asocial, woodchucks (Marmota monax) are behaviorally flexible marmots that exhibit greater sociality in some populations than others. I examined relationships between kinship, geographic distance, and home range overlap, as well as dispersal and philopatry, to determine the extent to which kin associated spatially. I used a combination of microsatellite DNA analysis, long-term behavioral observations, and radiotelemetry to test predictions that females, but not males, would associate with kin. Indeed, woodchucks lived closer and shared a greater proportion of their home range with more closely related animals. Overlap of females' and males' home ranges was positively correlated with kinship, and male–female dyads shared more area with closer kin. Most juveniles delayed dispersal beyond their first summer. Females often remained philopatric and settled near their natal range. Although males often dispersed as yearlings, some males also established territories within or immediately adjacent to their natal home ranges. A combination of factors can explain these spatial patterns, including high population density associated with the study site's location within a suburban environment, high dispersal costs, and abundant food. Thus, despite their asocial and solitary reputation, woodchucks displayed spatial patterns seen in other, more social species of ground-dwelling sciurids.     

Using simulation to explore the functional relationships of terrestrial carnivore population indices

Population indices based on visits to detection stations commonly are used to monitor wildlife populations. Inferences about populations are based on 1 of 2 measures: (1) change in the proportion of stations visited at least once or (2) change in the cumulative number of visits by unique individuals. The functional relationships between index responses and population density is poorly understood and can lead to misinterpretation of index data when an incorrect functional relationship (e.g. linear) is assumed. We created a flexible simulation environment to study the response of detection-based population indices under a wide variety of conditions meant to reflect species life history and study design. Proportional indices exhibited non-linear saturating responses to changes in population density while cumulative indices responded linearly. Shapes of responses were functions of home range sizes, individual detection probabilities, and spatial arrangement of animals and sampling stations. Non-linear relationships of proportional indices lead to under-estimation of mean population density when data are aggregated from multiple detection stations deployed in a heterogeneous landscape. Cumulative indices have significant statistical advantages over proportional indices including smaller sample sizes required to detect density change, linearity, consistent index responses across a wide range of densities, and ability to aggregate data to meet minimum sample size requirements. Our simulation provides a flexible tool for the interpretation of station-based population indices.     

Size and spatial arrangement of home range of checkered snapper <Emphasis Type="Italic">Lutjanus decussatus</Emphasis> (Lutjanidae) in an Okinawan coral reef determined using a portable GPS receiver

Although snappers (Lutjanidae) are commercially important fishery resources in tropical and subtropical waters, their home range size and its spatial arrangement have not been sufficiently clarified. In the present study, the size and spatial arrangement of the home range of the reef-associated checkered snapper Lutjanus decussatus (Lutjanidae) were investigated by use of a portable GPS receiver. In a 120 m × 120 m quadrat established on a section of the fringing reef of Ishigaki Island, 29 individuals of the species were identified by their color pattern and individuals were divided into five arbitrary size classes (class 1 <10 cm TL ≤ class 2 <15 cm TL ≤ class 3 <20 cm TL ≤ class 4 <25 cm TL ≤ class 5). Fish tracking by snorkeling was conducted with the portable GPS receiver. Site fidelity of this species was high. Home range size ranged from 93.0 to 3638.4 m², and there was a significant positive correlation between the home range size and fish total length. Home ranges of the same-sized individuals abutted each other (8.8% area overlap), whereas those of different-sized individuals overlapped (44.0% area overlap). Agonistic behavior (attack and agonistic display) was more frequently found among same-sized individuals (times of agonistic behavior/times of all encounters × 100 = 71.3%), whereas such agonistic behavior was rarely found among different-sized individuals (times of agonistic behavior/times of all encounters × 100 = 6.9%). These results suggest that home ranges of Lutjanus decussatus can be regarded as territories against same-sized individuals, but not different-sized individuals. The usefulness of the fish tracking by snorkeling using a portable GPS receiver for home range size estimation and the function of the overlapping territory of the species are discussed.     

Modelling landscape effects on density-contact rate relationships of deer in eastern Alberta: Implications for chronic wasting disease

Managing wildlife diseases requires an understanding of disease transmission, which may be strongly affected by host population density and landscape features. Transmission models are typically fit from time-series disease prevalence data and modelled based on how the contact rate among hosts is affected by density, which is often assumed to be a linear (density-dependent transmission) or constant (frequency-dependent transmission) relationship. However, long-term time-series data is unavailable for emerging diseases, and this approach cannot account for independent effects of landscape. We developed a mechanistic model based on ecological data to empirically derive the contact rate-density relationship in white-tailed and mule deer in an enzootic region of chronic wasting disease (CWD) in Alberta, Canada and to determine whether it was affected by landscape. Using data collected from aerial surveys and GPS-telemetry, we developed empirical relationships predicting deer group size, home range size, and habitat selection to iteratively simulate deer distributions across a range of densities and landscapes. We calculated a relative measure of total per-capita contact rate, which is proportional to the number of other deer contacted per individual per unit time, for each distribution as the sum of pairwise contact rates between a target deer and all other individuals. Each pairwise contact rate was estimated from an empirical relationship developed from GPS-telemetry data predicting pairwise contact rates as a function of home range overlap and landscape structure. Total per-capita contact rates increased as a saturating function of density, supporting a transmission model intermediate between density- and frequency-dependent transmission. This pattern resulted from group sizes that reached an asymptote with increasing deer density, although this relationship was mediated by tree and shrub coverage in the landscape, such that in heavily wooded areas, the contact rate saturated at much lower densities. These results suggest that CWD management based on herd reductions, which require a density-dependent contact rate to be effective, may have variable effects on disease across a single management region. The novel mechanistic approach we employed for estimating effects of density and landscape on transmission is a powerful complement to typical data-fitting approaches for modelling disease transmission.     

Simultaneous GPS tracking reveals male associations in a solitary carnivore

In hypercarnivorous species, females have large spatial requirements to meet their nutritional needs, and food competition among females is intense. As a result, females are typically solitary and territorial, and solitary males compete for access to dispersed females. Yet, largely anecdotal reports indicate that facultative male sociality may be more common in solitary carnivores than previously thought. We studied spatial interactions among fossas (Cryptoprocta ferox), Madagascar's largest carnivore, using simultaneous GPS tracking of 13 adult individuals to determine patterns of sex-specific spatial distribution and sociality. Male home ranges were larger than those of females, male home ranges overlapped more with those of other males than those of females with other females. Whereas some males were solitary, a subset of adult males was found to have very high home range overlap, high rates of co-location within <50 m, low minimum inter-individual distances, and significantly positive “dynamic interaction”. These associated dyads sometimes, but not always, were close relatives. The fact that solitary and associated males coexist in this population raises interesting questions concerning constraints and flexibility of social tolerance. This study yielded preliminary indications that female distribution appears to be primarily structured by resource competition, whereas male sociality seems to depend on demographic chance events, yet unknown proximate determinants of social tolerance, and it is associated with somatic and reproductive advantages. Male associations among carnivores are therefore more widespread and appear to be based on a wider range of factors than previously thought.     

Socially induced delayed primiparity in brown bears Ursus arctos

Reproductive suppression through behavioral or physiological means is common in group-living and cooperative breeding mammals, but to our knowledge it has not been shown in wild large carnivores other than those with a clear form of social organization. Brown bear (Ursus arctos) females form matrilinear assemblages with related females using a common and largely exclusive area. Behavioral reproductive suppression might develop due to a hierarchical system among females within a matrilinear assemblage or due to inbreeding avoidance, because male brown bears can overlap with their daughters. We tested whether natal dispersal influenced the age of primiparity. We predicted that emigrant females, geographically removed from maternal or paternal influence, would reproduce earlier than philopatric females. The average age of primiparity was 4.3 years in females that dispersed outside their mother’s home range (n=8) and 5.2 years in philopatric females (n=10). Only the overlap with the mother’s home range, and not body size, body mass, growth, local population density, or overlap with the father’s home range, had a significant influence on the age of primiparity. The ultimate role of reproductive suppression for brown bears is likely to avoid inbreeding or to minimize resource competition. Due to the low risk of inbreeding and frequent exposure of young females to unrelated males, we conclude that resource competition within female hierarchies causes reproductive suppression in young females.     

On the possible contribution of mixed species flocks to species richness in neotropical avifaunas

Summary Mixed species foraging flocks are a dominant component of the infra-structure of avian communities in neotropical forests. In Amazonia, these flocks consist of pairs of 10–20 species, many of which are permanently associated with mixed flocks. At least half of these flocking species maintain territories that correspond exactly to the flock home range. Small individuals that participate as permanent members of the flocks must adopt the large home range of the larger nucleus species. Therefore, the densities of smaller species are dependent on the availability and density of flocks rather than the availability of food resources. Single pairs of 4 small flocking species with individual body masses of 8 g occupied exclusive territories of 8–12 ha. These were the same exact territories that were defended by at least 6 other flocking species with individual body masses of up to 37 g. Because of their attachment to flocks with large territories, small species are expected to under-utilize available food resources. The under-utilization of food resources is expected to allow smaller species to coexist with greater niche overlap resulting in increased species richness. This hypothesis was tested by quantifying foraging niche in terms of foraging height, foraging maneuver, and prey substrate; and using these values in addition to body mass and bill size (length, depth and width) to determine relative niche overlap between large versus small species pairs.Smaller species had greater foraging overlap than large flocking species and particularly the three smallest species of the genus Myrmotherula; longipennis, axillaris and menetriesii had very high overlap (average foraging niche overlap for the 3 species=0.83±0.12 compared with 0.12±0.19 for all flocking species), similar body sizes (body masses differing by no more then 8%) and similar bill morphologies (maximum ratio in length=1.08, width=1.07, and depth=1.06). These results are consistent with the hypothesis that small species participating in Amazonian mixed flocks can coexist with greater niche overlap because their density is flock dependent rather than resource dependent.     

The nature and frequency of social interactions among free-living prairie voles (Microtus ochrogaster)

Hypotheses relating the behavior of voles to their population cycles often assume that the rate of social interaction increases with population density. To test this assumption, we examined the frequency of social interactions in a population of prairie voles (Microtus ochrogaster) over a 7-year period. In addition, we characterized space use by resident animals, patterns of visitation by nonresidents to nests, and participants in social interactions. Social groups within the population typically displayed little overlap in their use of space, even at high population densities. Nevertheless, nonresidents, particularly wandering males, were captured as visitors at nests. The number of visits per social group did not increase in a simple linear manner with population density and was particularly variable when there were fewer than 100 animals/ha. At such times, more single females and fewer pairs received visits from males than expected based on the frequency of occurrence of these groups in the population; a similar pattern was noted during periods of high population density (≥100 animals/ha) but the comparisons failed to reach statistical significance. Furthermore, at high population density, more communal groups received visits from females than expected. Patterns of visitation to communal groups were influenced by the number of adult male residents (winter only), but not by the number of adult female residents or presence of philopatric female offspring. These data indicate that the frequency of social contact in prairie voles does not increase linearly with population density and is influenced by the spacing and possible mate-guarding behavior of resident animals. Received: 7 January 1998 / Accepted after revision: 16 May 1998     

Should consumptive sustainable use of Sika Deer (Ceruus nippon) in Dilijan Reserve,NE Armenia be instituted?

SUMMARY

Numbers of sika deer (Ceruus nippon), resident in the Dilijan Reserve in 1969 (52 animals), 1970 (50), 1972 (1), and 1976 (28) dramatically increased in number until 1981, when the population reached a ceiling, being the number which can subsist in the area—300 individuals (density—11–12.5 deer per 1000 ha). Thus, Dilijan Reserve's C. nippon population develops in a way which resembles an S-like log curve equation.

Actually, Dilijan Reserve no longer has the status of a protected area—nowadays lumbering activities predominate and, inevitably, the unique broadleaf deciduous forest ecosystem will run down to extinction. Such economically valuable species as oak, beech, and sika deer are likely to be the first victims of this large-scale devastation.

The present article does not reject exploitation of any resource (including sika deer), if necessary. The key question is: how C. nippon can be sustainably utilized, so that the number of culled animals is replenished within the same year and and so that eventually the population size will remain constant?     

Spatiotemporal dynamics of habitat use by koalas: the checkerboard model

Animal movement patterns and use of space depend upon food and nonfood resources, as well as conspecific and heterospecific interactions, but models of habitat use often neglect to examine multiple factors and rarely include marsupials. We studied habitat use in an Australian population of koalas (Phascolarctos cinereus) over a 6-year period in order to determine how koalas navigate their environment and partition limited patchy food and nonfood resources. Tree selection among koalas appears to be mediated by folar chemistry, but nonfood tree selection exerts a major impact on home range use due to thermoregulatory constraints. Koalas moved on a daily basis, during both day and night, but daytime resting site was not necessarily in the same location as nighttime feeding site. Koalas had substantial home range overlap in the near absence of resource sharing with less than 1% of trees located in areas of overlap used by multiple koalas. We suggest that koala spatiotemporal distribution and habitat use are probably based upon a community structure of individuals, with a checkerboard model best describing overlap in home range area but not in resource use. Nonfood refugia and social networks should be incorporated into models of animal range and habitat use.     

Use of Spatial Capture‐Recapture Modeling and DNA Data to Estimate Densities of Elusive Animals

Abstract: Assessment of abundance, survival, recruitment rates, and density (i.e., population assessment) is especially challenging for elusive species most in need of protection (e.g., rare carnivores). Individual identification methods, such as DNA sampling, provide ways of studying such species efficiently and noninvasively. Additionally, statistical methods that correct for undetected animals and account for locations where animals are captured are available to efficiently estimate density and other demographic parameters. We collected hair samples of European wildcat (Felis silvestris) from cheek‐rub lure sticks, extracted DNA from the samples, and identified each animals’ genotype. To estimate the density of wildcats, we used Bayesian inference in a spatial capture‐recapture model. We used WinBUGS to fit a model that accounted for differences in detection probability among individuals and seasons and between two lure arrays. We detected 21 individual wildcats (including possible hybrids) 47 times. Wildcat density was estimated at 0.29/km² (SE 0.06), and 95% of the activity of wildcats was estimated to occur within 1.83 km from their home‐range center. Lures located systematically were associated with a greater number of detections than lures placed in a cell on the basis of expert opinion. Detection probability of individual cats was greatest in late March. Our model is a generalized linear mixed model; hence, it can be easily extended, for instance, to incorporate trap‐ and individual‐level covariates. We believe that the combined use of noninvasive sampling techniques and spatial capture‐recapture models will improve population assessments, especially for rare and elusive animals.