Effects of Human Harvesting, Residences, and Forage Abundance on Deer Spatial Distribution

It has been known that harvesting by humans strongly influences individual within-home range habitat selection of many deer species; however, little is known about the effect of harvesting on coarse-scale habitat selection (i.e., spatial distribution). We examined the summer spatial distribution of sika deer Cervus nippon in relation to human harvesting and other factors, such as human residences, forage abundance, and cover, using pellet group counts at Mount Fuji, central Japan, in 2018. In the study area, harvesting is conducted at medium elevation areas throughout the year, but not at high or low elevation areas where access is difficult or harvesting is prohibited. Spatial distribution of deer was significantly biased to non-harvesting areas and far from residential areas, suggesting that they avoid riskier spaces by establishing a landscape of fear. High-quality food resources (deciduous broad-leaved trees and forbs) were more abundant in harvesting areas than in non-harvesting areas, suggesting that foraging pressure by deer reduce them. However, there were no differences in abundances of more fibrous dwarf bamboo between harvesting and non-harvesting areas, and spatial distribution of deer was significantly biased to higher dwarf bamboo abundance areas, suggesting that the dwarf bamboo is an alternative food resource in non-harvesting areas where supplies of high-quality food were limited. Our results suggest that human harvesting pressure and residences shifted the spatial distribution of deer from the montane forests to subalpine/alpine zones, which may increase damage to vulnerable ecosystems due to severe foraging pressure.

Diversity begets stability: Sublinear growth and competitive coexistence across ecosystems

The worldwide loss of species diversity brings urgency to understanding how diverse ecosystems maintain stability. Whereas early ecological ideas and classic observations suggested that stability increases with diversity, ecological theory makes the opposite prediction, leading to the long-standing "diversity-stability debate." Here, we show that this puzzle can be resolved if growth scales as a sublinear power law with biomass (exponent <1), exhibiting a form of population self-regulation analogous to models of individual ontogeny. We show that competitive interactions among populations with sublinear growth do not lead to exclusion, as occurs with logistic growth, but instead promote stability at higher diversity. Our model realigns theory with classic observations and predicts large-scale macroecological patterns. However, it makes an unsettling prediction: Biodiversity loss may accelerate the destabilization of ecosystems.

Context-dependent group size: effects of population density, habitat, and season

Group size can vary in relation to population density, habitat, and season. Habitat and season may also interact with population density and affect group size through varying foraging benefits of social aggregation in different ecological contexts. We tested the hypothesis that group size varies across ecological contexts, including population density, habitat type, and season, for woodland caribou (Rangifer tarandus) in ten herds over 25 years in Newfoundland, Canada. We predicted that group size would increase as a function of population density. Based on the foraging benefits of social aggregation, we predicted larger groups as habitat openness increased because open areas tend to have higher quality foraging resources. We predicted larger groups during winter when foraging resources are covered in snow because caribou and other social animals exploit social information about the location of foraging resources. In contrast to our prediction, group size decreased as a function of population density. In support of our prediction, group size was larger in winter than calving and summer, and we found that group size increased with habitat openness in some, but not all, cases. Patterns of animal grouping are context-dependent and the additive effect of different ecological contexts on variation in group size informs our understanding of the implicit trade-offs between competition, predation risk, and profitability of forage.

Hunger mediates apex predator's risk avoidance response in wildland-urban interface

Conflicts between large mammalian predators and humans present a challenge to conservation efforts, as these events drive human attitudes and policies concerning predator species. Unfortunately, generalities portrayed in many empirical carnivore landscape selection studies do not provide an explanation for a predator's occasional use of residential development preceding a carnivore-human conflict event. In some cases, predators may perceive residential development as a risk-reward trade-off. We examine whether state-dependent mortality risk-sensitive foraging can explain an apex carnivore's (Puma concolor) occasional utilization of residential areas. We assess whether puma balance the risk and rewards in a system characterized by a gradient of housing densities ranging from wildland to suburban. Puma GPS location data, characterized as hunting and feeding locations, were used to assess landscape variables governing hunting success and hunting site selection. Hunting site selection behaviour was then analysed conditional on indicators of hunger state. Residential development provided a high energetic reward to puma based on increases in prey availability and hunting success rates associated with increased housing density. Despite a higher energetic reward, hunting site selection analysis indicated that pumas generally avoided residential development, a landscape type attributed with higher puma mortality risk. However, when a puma experienced periods of extended hunger, risk avoidance behaviour towards housing waned. This study demonstrates that an apex carnivore faces a trade-off between acquiring energetic rewards and avoiding risks associated with human housing. Periods of hunger can help explain an apex predator's occasional use of developed landscapes and thus the rare conflicts in the wildland-urban interface. Apex carnivore movement behaviours in relation to human conflicts are best understood as a three-player community-level interaction incorporating wild prey distribution.

Group or ungroup - moose behavioural response to recolonization of wolves

Background

Predation risk is a primary motivator for prey to congregate in larger groups. A large group can be beneficial to detect predators, share predation risk among individuals and cause confusion for an attacking predator. However, forming large groups also has disadvantages like higher detection and attack rates of predators or interspecific competition. With the current recolonization of wolves (Canis lupus) in Scandinavia, we studied whether moose (Alces alces) respond by changing grouping behaviour as an anti-predatory strategy and that this change should be related to the duration of wolf presence within the local moose population. In particular, as females with calves are most vulnerable to predation risk, they should be more likely to alter behaviour.

Methods

To study grouping behaviour, we used aerial observations of moose (n = 1335, where each observation included one or several moose) inside and outside wolf territories.

Results

Moose mostly stayed solitary or in small groups (82% of the observations consisted of less than three adult moose), and this behavior was independent of wolf presence. The results did not provide unequivocal support for our main hypothesis of an overall change in grouping behaviour in the moose population in response to wolf presence. Other variables such as moose density, snow depth and adult sex ratio of the group were overall more influential on grouping behaviour. However, the results showed a sex specific difference in social grouping in relation to wolf presence where males tended to form larger groups inside as compared to outside wolf territories. For male moose, population- and environmentally related variables were also important for the pattern of grouping.

Conclusions

The results did not give support for that wolf recolonization has resulted in an overall change in moose grouping behaviour. If indeed wolf-induced effects do exist, they may be difficult to discern because the effects from moose population and environmental factors may be stronger than any change in anti-predator behaviour. Our results thereby suggest that caution should be taken as to generalize about the effects of returning predators on the grouping behaviour of their prey.

Electronic supplementary material

The online version of this article (doi:10.1186/s12983-017-0195-z) contains supplementary material, which is available to authorized users.

Density-dependent diel activity in stream-dwelling Arctic charr Salvelinus alpinus

Intraspecific competition plays a significant role in shaping how animals use and share habitats in space and time. However, the way individuals may modify their diel activity in response to increased competition has received limited attention. We used juvenile (age 1+) Arctic charr Salvelinus alpinus to test the prediction that individuals at high population density are more active and distribute their foraging activity over a greater portion of the 24-h cycle than individuals at low population density. Individually tagged fish were stocked in seminatural stream enclosures at low (2 fish/m(2)) and high (6 fish/m(2)) density. During each of two 2-week experimental rounds, activity of all fish within each enclosure was recorded every 3 h over seven 24-h cycles. At high density, fish were more active and distributed their activity over a greater portion of the 24-h cycle, with increased activity particularly at crepuscular times. Fluctuations in ecological conditions (e.g., water temperature and light intensity) also affected activity. Fish at high density grew as fast as fish at low density. This study demonstrates that individuals exhibit a degree of behavioral flexibility in their response to changes in ecological conditions and suggests that intraspecific competition can cause animals to modify temporal aspects of their activity to gain access to resources and maintain growth.

Daily, seasonal, and annual variations in individual home-range overlap of two sympatric species of deer

Behavioural tactics of animals are determined by both environmental and social factors. Among nonmigratory ungulates, most home-range studies focused either on the effect of environmental variables on home-range size or on the overlap between home ranges of different individuals. Here, as rarely in previous studies, we aim to identify the dynamics of the home range of a given individual, involving variation in home-range size and home-range overlap between periods, for two resident populations of contrasting species: red deer (Cervus elaphus L., 1758) and roe deer (Capreolus capreolus (L., 1758)). In both species, yearly and seasonal home-range fidelity was high and constant (mean of 64% in red deer and mean of 66% in roe deer), possibly because of benefits accruing from knowledge of spatial distribution of food resources and refugia. Home range in winter, when food availability was low, was larger than other seasonal home ranges for both species. Differences in body size between red deer and roe deer accounted for observed between-species differences in space use, especially when the species were active at night. Our study clearly demonstrates that patterns of variation in home-range size are similar; however, between-species differences in body size lead to differential patterns of home-range size and fidelity.

Toward an identification of resources influencing habitat use in a multi-specific context

Interactions between animal behaviour and the environment are both shaping observed habitat use. Despite the importance of inter-specific interactions on the habitat use performed by individuals, most previous analyses have focused on case studies of single species. By focusing on two sympatric populations of large herbivores with contrasting body size, we went one step beyond by studying variation in home range size and identifying the factors involved in such variation, to define how habitat features such as resource heterogeneity, resource quality, and openness created by hurricane or forest managers, and constraints may influence habitat use at the individual level. We found a large variability among individual's home range size in both species, particularly in summer. Season appeared as the most important factor accounting for observed variation in home range size. Regarding habitat features, we found that (i) the proportion of area damaged by the hurricane was the only habitat component that inversely influenced roe deer home range size, (ii) this habitat type also influenced both diurnal and nocturnal red deer home range sizes, (iii) home range size of red deer during the day was inversely influenced by the biomass of their preferred plants, as were both diurnal and nocturnal core areas of the red deer home range, and (iv) we do not find any effect of resource heterogeneity on home range size in any case. Our results suggest that a particular habitat type (i.e. areas damaged by hurricane) can be used by individuals of sympatric species because it brings both protected and dietary resources. Thus, it is necessary to maintain the openness of these areas and to keep animal density quite low as observed in these hunted populations to limit competition between these sympatric populations of herbivores.

The impact of sika deer grazing on the vegetation and infauna of Arne saltmarsh

Arne saltmarsh, an RSPB reserve, is situated in Poole Harbour on the English south coast. In recent years, there has been concern about possible changes in the suitability of the site for Redshank (Trigna totanus) due to sika deer (Cervus nippon) grazing. In order to assess these changes, 50 plots were established in three different locations: 20 in grazed areas, 20 in ungrazed areas and 10 fenced enclosures. Deer grazing was found to significantly affect structural and species diversity of the saltmarsh vegetation. Spartina anglica dominated in ungrazed areas whilst Salicornia ramosissima and, to a lesser extent, Puccinellia maritima dominated in grazed sites. In grazed areas the vegetation cover was significantly lower, as was vegetation height and volume. In addition, significant changes were observed in the root biomass, which was lower in grazed areas. Infaunal diversity was generally low throughout the survey area. However, significant variations were observed. Invertebrates abundance was more abundant in grazed plots than in ungrazed plots, and least abundant in fenced plots. The study indicated that in its current condition, localised areas of Arne saltmarsh do not provide adequate habitat requirements for Tringa totanus.

Group composition and cohesion in sympatric white-tailed deer and mule deer

White-tailed deer (Odocoileus virginianus) have been reported to live in smaller groups than mule deer (Odocoileus hemionus). Group size, however, generally varies with habitat conditions, and no comparison has been made between the social structures of the two species living in the same ecological conditions. I compared the size, composition, and stability of groups formed by sympatric whitetails and mule deer living in a prairie habitat in southern Alberta. Seasonal trends were similar for the two species. Females and fawns usually formed small groups during summer. Larger mixed-sex groups became increasingly common during winter, well after the breeding season. Despite the similar seasonal trend, mule deer were significantly more likely than whitetails to occur in relatively large groups composed of both sexes during winter, and whitetails were more likely to occur in small female groups. Mule deer groups were more stable than whitetail groups, and marked mule deer fawns developed strong associations with other known fawns. Habitat variation was limited and was not related to group size. These results show that the composition and cohesion of whitetail and mule deer groups differ, even when the species live in similar circumstances. The differences in grouping behaviour, larger more cohesive groups formed by mule deer than by whitetails, are consistent with those expected to result from the selection pressure of predation.

Herd size in large herbivores: encoded in the individual or emergent?

In large mammalian herbivores, the increase of group size with habitat openness was first assumed to be an adaptive response, encoded in the individual. However, it could, alternatively, be an emergent property: if groups were nonpermanent units, often fusing and splitting up, then any increase of the distance at which animals perceive one another could increase the rate of group fusion and thus mean group size. Dynamical models and empirical data support this second hypothesis. This is not to say that adaptive modifications of mean herd size cannot occur. However, this changes the way in which we can envisage the history of gregariousness in large herbivores during the Tertiary.

Effects of elk group size on predation by wolves

Wolf-prey research has focused on single-prey systems in North America dominated by moose (Alces alces) or white-tailed deer (Odocoileus virginianus). Elk (Cervus elaphus) are social ungulates and the main prey item of wolves (Canis lupus) in Banff National Park (BNP), Alberta. Grouping behaviour may affect the functional response of predators by changing how predators encounter and kill prey. We studied wolf predation on elk in BNP during the winters of 1997–1998 and 1998–1999 and tested how elk group size affected the availability of and encounter rates with elk groups and attack success of wolves. Wolves encountered larger elk groups than expected based on availability, and killed more elk from large groups than expected based on numbers of encounters. Elk group size increased with elk density in BNP. Increased rates of encounter with and success of attacking large elk groups, and the positive group size – density relationship may be a mechanism for density-dependent predation. We developed a predation-risk model to test the prediction that grouping will benefit individual elk, given this predation regime. Elk appeared to adopt two different strategies to minimize predation risk: living in small herds that were rarely encountered by wolves or living in large herds that reduced their predation risk through dilution.