Modelling the Relative Abundance of Roe Deer (Capreolus capreolus L.) along a Climate and Land-Use Gradient

European roe deer (Capreolus capreolus L.) are important given their economic, recreational and ecological value. However, uncontrolled roe deer numbers can result in negative impacts on forest regeneration and agricultural crops, disease transmission and occurrences of deer-vehicle collisions. Information on the abundance and distribution is needed for effective management. We combined distance sampling (DS) of roe deer dung pellet groups with multiple variables to develop a density surface model (DSM) in the federal state of Bavaria in south-eastern Germany. We used the estimates of pellet group density as a proxy for roe deer relative abundance. We extrapolated our best DSM, conducted a quantitative evaluation and contrasted relative abundance along climate and land-use gradients. Relative abundance of roe deer was influenced by a combination of habitat type, climate and wildlife management variables, which differed between seasons and which reflected changes in food and shelter availability. At the landscape scale, the highest abundance was observed in agriculture-dominated areas and the lowest in urban areas. Higher abundance was also observed in areas with intermediate temperatures compared to the warmest areas. Our results provide information on possible future changes in the distribution of relative abundance due to changes in climate and land-use.

Breeding dynamics of overabundant koala (Phascolarctos cinereus) populations subject to fertility-control management

Abstract ContextThe koala (Phascolarctos cinereus) sometimes occurs as an overabundant folivore in south-eastern Australia, where high-density populations have caused defoliation of preferred food trees, threatening habitat. Kangaroo Island, South Australia and Budj Bim National Park, Victoria, are two regions where such eruptive population dynamics have arisen. One way of mitigating their damage is through management via fertility control. AimsThis paper examines the outcomes of fertility control (surgical sterilisation and treatment with levonorgestrel implants) on breeding dynamics at the population level, using data obtained from two separate koala management programs conducted by State Government wildlife agencies, South Australia Department for Environment and Water and Parks Victoria. MethodsThe relationships between female body condition, reproductive status, fertility control, age and population density were examined using linear mixed effects models. Population density (koalas/ha) was estimated using annual census data and modelled in a Bayesian framework. Key resultsBody condition was a key influence on breeding success in female koalas, with sexual maturity being defined by both age and body condition, whereas the effect of reproductive experience was minimal. It is likely that reduced densities have led to decreased intraspecific competition for food resources and territory, leading to increased breeding success at one management site (BBNP) and by allowing females to begin breeding at a lower overall body condition. The reduction in densities to sustainable levels at both management sites, despite differing fertility-control methods, supports the use of the less invasive and more cost-effective levonorgestrel implants as the preferred fertility-control method. ConclusionsIn addition to contraceptive effects, broad-scale fertility control may have resulted in a compensatory higher breeding success in the untreated population, possibly in response to decreasing densities, increased resource availability or behavioural responses to population management. ImplicationsAlthough compensatory breeding mechanisms can reduce the effectiveness of fertility control at the population level, ongoing fertility-control management can still be successful at reducing overabundant koala populations to sustainable levels with significant long-term commitment, provided that annual control targets are continuously met.

Dear deer? Maybe for now. People's perception on red deer (Cervus elaphus) populations in Portugal

The human dimension of wildlife is a subject of increasing interest, especially considering the potential impact of people's perceptions on decision-making concerning wildlife management and thus on species' distribution and abundance. This is particularly important for species that inhabit human-dominated landscapes, where conflicts are likely to arise. These conflicts typically emerge between different human collectives when their interests collide and thus an assessment of their perceptions is valuable. Throughout Europe, ungulates have expanded, and Portugal is no exception. The expansion of red deer (Cervus elaphus) comes with benefits (e.g. hunting opportunities), but also with costs (e.g. vehicle collision or damage to crops), that can shape people's perceptions of these populations. To assess perceptions of red deer populations in continental Portugal, we developed a questionnaire survey with three interest groups: general public, farmers and hunters (total n = 1532). Our results show that perceptions about red deer were generally positive with a high acknowledgement of deer benefits, which we link to a broad level of sympathy towards this species. In addition, farmers showed a higher concern with crop damage caused by deer than non-farmers. Nonetheless, a general lack of knowledge regarding wildlife was present, particularly among younger people, who are potentially more apart and disconnected from nature. Now is the time to implement preventive and mitigation measures - e.g. fencing, reduction of population density - which can be a small contribution to address this problem. The focus should be put on people's acceptance of the required strategies to manage deer populations (which can also include unpopular practices, such as hunting). For that, an evaluation of people's attitudes towards deer populations and awareness of associated problems is essential. People's opinions, as well as the success of monitoring and management strategies, should be evaluated through multi-disciplinary teams, that include natural and social scientists, to ensure their success.

Harvest Programs in First Nations of Subarctic Canada: The Benefits Go Beyond Addressing Food Security and Environmental Sustainability Issues

By breaking down barriers that impacted the ability of subarctic First Nations people to harvest waterfowl, the Sharing-the-Harvest program provided a safe, nutritious, and culturally appropriate food (i.e., geese) to James Bay Cree communities while also helping to protect the environment by harvesting overabundant geese. However, the impacts extend beyond those described above. Thus, the objectives of the present paper are twofold: to document the food sharing networks of the Sharing-the-Harvest program; and to examine the benefits associated with the harvest program beyond food security and environmental sustainability issues, as revealed through semi-directed interviews. In the regional initiative, harvested geese were shared with all James Bay communities; sharing is an important part of Cree culture. Where detailed information was collected, the goose-sharing network reached 76% of the homes in one of the communities. Likewise, in the local initiative, the goose-sharing network had a 76% coverage rate of the homes in the community. Although decreasing food insecurity was an important focus of the harvest-sharing programs, there were other benefits, from an Indigenous perspective, of being on the land, as identified by the Cree harvesters through semi-directed interviews (e.g., the transmission of Indigenous knowledge, the strengthening of social networks, and the feeling of wellness while out on-the-land). Thus, by participating in the on-the-land harvest programs, the Cree gained benefits beyond those solely related to strengthening food security and contributing in part to environmental sustainability. The Sharing-the-Harvest protocol has the potential to be adapted and employed by other Indigenous (or marginalized) groups worldwide, to help improve health and wellness, while, also protecting the environment from overabundant and/or invasive species.

Addressing social attitudes toward lethal control of wildlife in national parks

The extraordinary population growth of certain ungulate species is increasingly a concern in agroforestry areas because overabundance may negatively affect natural environments and human livelihoods. However, society may have negative perceptions of killing wildlife to reduce their numbers and mitigate damage. We used an online survey that included a choice experiment to determine Spanish citizens' (n = 190) preferences toward wildlife population control measures related to negative effects of ungulate overabundance (negative impacts on vegetation and other wildlife species and disease transmission to livestock) in 2 agroforestry national parks in Spain. We used latent-class and willingness-to-pay in space models to analyze survey results. Two percent of respondents thought a national park should have no human intervention even if lack of management may cause environmental degradation, whereas 95% of respondents favored efforts to reduce damage caused by overabundant ungulate species. We estimated human well-being losses of survey respondents when sustainable effects of deer overabundance on the environment became unsustainable effects and well-being gains when sustainable effects transitioned to no visible effects. We found that the type of wildlife-control program was a very relevant issue for the respondents; indirect control in which killing was avoided was the preferred action. Sixty-six percent of respondents agreed with the option of hunters paying for culling animals to reduce ungulate impacts rather than management cost coming out of taxes, whereas 19% of respondents were against this option and willing to pay for other solutions in national parks. Our results suggest that killing wildlife in national parks could be a socially acceptable tool to manage overabundance problems in certain contexts, but it could also generate social conflicts.

A systematic review of ground-based shooting to control overabundant mammal populations

Abstract Context Ground-based shooting is widely used in management programs aiming to alleviate the impacts of invasive or overabundant wildlife populations. However, evaluations of individual shooting operations have shown variable results, and the effectiveness of ground-shooting as a population-management intervention has not been systematically examined. Aims Our review aimed to (1) assess the efficacy of shooting as a population management tool, and (2) identify commonalities among studies that will help managers identify situations where ground-shooting is most likely to be effective. Methods We systematically reviewed the literature to identify studies involving ground-shooting. From each study, we collated information about operational objectives, target taxa, geographic context, type of shooter used, effort, effectiveness, and use of additional control tools. Key results Most studies had no a priori quantifiable objectives. However, 60% of the 64 case studies produced a detectable reduction in population density and/or damage. The most common type of operation used unpaid or commercial harvest-oriented shooters to reduce herbivore density or damage. Only 30% of the operations that used volunteer shooters or recreational hunters achieved their objectives. Target taxa, geographic area or integration of shooting with other population-control methods had no detectable effect on the effectiveness of shooting operations. Common factors that hindered the effectiveness of shooting operations included immigration of target species from adjacent areas (n=13), decreasing effort from shooters as the target population declined (n=7) and selective harvesting (n=7). Conclusions Ground-based shooting can be an effective management tool for overabundant wildlife populations, but many shooting operations did not achieve a notable decrease in animal abundance or damage. The source of failure could often be attributed to an inability to remove a sufficient proportion of the population to cause a population decline. Implications Managers contemplating using ground-based shooting to reduce the impacts or density of wildlife populations should (1) carefully consider whether this is a suitable management tool to achieve the desired outcomes, (2) establish clear objectives that aim to meet defined outcomes and allow for continuous improvement, and (3) ensure that operations are sufficiently resourced to achieve and maintain those objectives.

Compassionate versus consequentialist conservation

Ethical treatment of wildlife and consideration of animal welfare have become important themes in conservation, but ethical perspectives on how best to protect wild animals and promote their welfare are diverse. There are advantages to the consequentialist harms ethical framework applied in managing wild herbivores for conservation purposes. To minimize harms while achieving conservation goals, we argue that overabundant wild herbivores should in many cases be managed through consumptive in situ killing. Advantages of this policy are that the negative welfare states imposed on animals last only a short time; remaining animals are not deprived of positive welfare states (e.g., linked to rearing offspring); poor welfare states of animals in overabundant populations are avoided (e.g., starvation); negative welfare impacts on heterospecifics through resource depletion (i.e., competition) are prevented; harvesting meat reduces the number of (agricultural) animals raised to supply meat; and minimal costs maximize funding for other wildlife management and conservation priorities. Alternative ethical approaches to our consequentialist framework include deontology (containing animal rights) and virtue ethics, some of which underpin compassionate conservation. These alternative ethical approaches emphasize the importance of avoiding intentional killing of animals but, if no population reduction occurs, are likely to impose considerable unintentional harms on overabundant wildlife and indirectly harm heterospecifics through ineffective population reduction. If nonlethal control is used, it is likely that overabundant animals would be deprived of positive welfare states and economic costs would be prohibitive. We encourage conservation stakeholders to consider animal-welfare consequentialism as an ethical approach to minimize harms to the animals under their care as well as other animals that policies may affect while at the same time pursuing conservation goals.

Patch-scale culls of an overabundant bird defeated by immediate recolonization

Overabundant native animals cause a variety of human-wildlife conflicts that can require management to reduce their social, environmental, or economic impacts. Culling is an intuitively attractive management response to overabundance, but poor monitoring of results and costs means that evidence for successful outcomes is often lacking. Furthermore, many culls worldwide have been ineffective or counterproductive due to ecological release mechanisms or compensatory responses by the overabundant species. We completed a controlled, replicated, costed, and rigorously monitored experimental cull of the endemic Australian honeyeater, the Noisy Miner (Manorina melanocephala). Aggressive exclusion of birds from remnant woodland patches by overabundant Noisy Miners is listed as a Key Threatening Process under Australian conservation legislation due to its impacts on threatened birds. The problem is particularly prevalent in the highly modified agricultural landscapes of eastern Australia. The species impacts avian assemblages at low densities (0.6-0.8 birds/ha) and at a subcontinental scale (>1 million km² ). Some ecologists recommend culling as the only management response capable of timely reversal of declines of threatened small woodland birds. We monitored Noisy Miner abundance before and for 12 months after a culling program and found that immediate recolonization from the surrounding landscape negated the impact of the cull. We hypothesize that this is due to a vacuum effect; whereby, birds resident in more marginal habitat around treatment patches move into the vacant territory post-cull. Modeled mean abundance of Noisy Miners declined by 22% in treatment sites compared to an increase of 4% in control sites in the post-cull period. Abundance in all sites, however, remained three to five times higher than published ecological impact thresholds. Return on investment analysis indicated no relationship between culling effort and reduction in Noisy Miner abundance. We conclude that culling at a patch scale is not an efficient method of reducing Noisy Miner abundance to levels unlikely to impact threatened woodland birds in the highly modified study landscape, despite estimated costs 18 times lower than another potential management response of revegetation. Our study highlights the importance of building empirical evidence before intuitively attractive but not necessarily ecologically effective management responses are applied more widely.

Integrating theory into disturbance interaction experiments to better inform ecosystem management

Managing multiple, interacting disturbances is a key challenge to biodiversity conservation, and one that will only increase as global change drivers continue to alter disturbance regimes. Theoretical studies have highlighted the importance of a mechanistic understanding of stressor interactions for improving the prediction and management of interactive effects. However, many conservation studies are not designed or interpreted in the context of theory and instead focus on case-specific management questions. This is a problem as it means that few studies test the relationships highlighted in theoretical models as being important for ecological management. We explore the extent of this problem among studies of interacting disturbances by reviewing recent experimental studies of the interaction between fire and grazing in terrestrial ecosystems. Interactions between fire and grazing can occur via a number of pathways; one disturbance can modify the other's likelihood, intensity or spatial distribution, or one disturbance can alter the other's impacts on individual organisms. The strength of such interactions will vary depending on disturbance attributes (e.g. size or intensity), and this variation is likely to be nonlinear. We show that few experiments testing fire-grazing interactions are able to identify the mechanistic pathway driving an observed interaction, and most are unable to detect nonlinear effects. We demonstrate how these limitations compromise the ability of experimental studies to effectively inform ecological management. We propose a series of adjustments to the design of disturbance interaction experiments that would enable tests of key theoretical pathways and provide the deeper ecological understanding necessary for effective management. Such considerations are relevant to studies of a broad range of ecological interactions and are critical to informing the management of disturbance regimes in the context of accelerating global change.

A systematic review of the impacts and management of introduced deer (family Cervidae) in Australia

Deer are among the world’s most successful invasive mammals and can have substantial deleterious impacts on natural and agricultural ecosystems. Six species have established wild populations in Australia, and the distributions and abundances of some species are increasing. Approaches to managing wild deer in Australia are diverse and complex, with some populations managed as ‘game’ and others as ‘pests’. Implementation of cost-effective management strategies that account for this complexity is hindered by a lack of knowledge of the nature, extent and severity of deer impacts. To clarify the knowledge base and identify research needs, we conducted a systematic review of the impacts and management of wild deer in Australia. Most wild deer are in south-eastern Australia, but bioclimatic analysis suggested that four species are well suited to the tropical and subtropical climates of northern Australia. Deer could potentially occupy most of the continent, including parts of the arid interior. The most significant impacts are likely to occur through direct effects of herbivory, with potentially cascading indirect effects on fauna and ecosystem processes. However, evidence of impacts in Australia is largely observational, and few studies have experimentally partitioned the impacts of deer from those of sympatric native and other introduced herbivores. Furthermore, there has been little rigorous testing of the efficacy of deer management in Australia, and our understanding of the deer ecology required to guide deer management is limited. We identified the following six priority research areas: (i) identifying long-term changes in plant communities caused by deer; (ii) understanding interactions with other fauna; (iii) measuring impacts on water quality; (iv) assessing economic impacts on agriculture (including as disease vectors); (v) evaluating efficacy of management for mitigating deer impacts; and (vi) quantifying changes in distribution and abundance. Addressing these knowledge gaps will assist the development and prioritisation of cost-effective management strategies and help increase stakeholder support for managing the impacts of deer on Australian ecosystems.

Short-term effects of hunting on naïve black-tailed deer (Odocoileus hemionus sitkensis): behavioural response and consequences on vegetation growth

Hunting is commonly used to reduce overabundant deer populations that are of socioeconomic and ecological concerns. Recently, it has been suggested that “hunting for fear” might help maximize nonconsumptive effects of hunting and their cascading impacts. We investigated how a predator-free black-tailed deer (Odocoileus hemionus sitkensis Merriam, 1898) population introduced to the Haida Gwaii archipelago (Canada) responded to short-term hunting for fear. We conducted a hunt that minimized killing and maximized scaring on an island where some deer were marked. Between control and hunted sites, we compared deer use of bait stations and of shoreline areas (i.e., an open and risky area that provided marine subsidies). We also compared the browsing pressure and growth of two grasses and two shrubs. Hunting for fear had no effect on the overall use of bait stations and shorelines. However, in the area exposed to hunting, unmarked deer, which were assumed to be less tolerant of human disturbance, avoided bait stations at the outset of hunting. We concluded that individuals perceive and respond to risk differently. Furthermore, two of the four plant species were less likely to be browsed and had better growth in the experimental area than in the control area, suggesting an indirect effect of hunting on plants mediated by deer behaviour.

Autumn-winter diet overlap of fallow, red, and roe deer in forest ecosystems, Southern Poland

The wild population of fallow deer in Central Europe has grown considerably over the last decade. However, information on feeding habits of this alien species in relation to the indigenous red deer or roe deer, in areas of their co-occurrence, is scarce. A prevailing view maintains that their food-niches are distinct, although direct comparative studies have not been carried out. Therefore, the aim of the research was to compare the diets of fallow, red, and roe deer feeding in the same habitat. Research was based on the rumen contents of 242 animals hunted in the autumn-winter season in the forests of Southern Poland. The analyses demonstrated that fallow deer are moderate grazers in such conditions and eat more graminoids in comparison to red or roe deer (36.4% vs. 16.1% or 5.5%, respectively). On the other hand, it feeds on less browse (17.2% vs. 41.4%) or dwarf shrubs (8.4% vs. 19.0%) than red deer, and on less bramble (10.9% vs. 34.6%) or forbs (4.0% vs. 7.6%) in comparison to roe deer (P=0.05). Although the diets of the three deer species differ in terms of the proportion of each food type in their diet, overlapping of their food-niches is high (52.6%).

A review of introduced cervids in Chile

We review the extent of exotic deer distributions in Chile, which are encountered in all provinces, including Tierra del Fuego, except for possibly Region III; many deer are contained in at least 107 enclosures. Red deer (Cervus elaphus) by far has the largest feral population of exotic cervids in southern South America, providing source animals that can easily cross the Andes between Chile and Argentina. Red deer was introduced from Europe to the central valley of Chile in 1928. Since the 1940s, feral populations have also expanded from Argentina into Chile, by way of easily accessible, low-elevation mountain passes of the Andes, accompanied by further direct shipments from Argentina. The area occupied by 1990 was estimated at 3400 km2, whereas an analysis in 2003 estimated an area of 7700 km2. The overall area invaded by 2003 was between 37°42′S and 54°55′S, and 73°36′W and 69°50′W (Argentina and Chile combined, although non-contiguous). Ecological impact of the red deer in Chile has been described since 1981, and red deer features in the Chilean Pest Manual. A conservative rate for the red deer expansion was estimated at 1 km/year, but likely is more rapid where habitat modifications facilitate movement. The pre-Columbian northern limit of the native cervid huemul (Hippocamelus bisulcus) was 30°S, and because red deer has occupied all habitat types currently used by huemul, it could thus spread >750 km further north. To the south, all areas are suitable for red deer. Invasion patterns will depend on additional intentional introductions and enclosures on both sides of the Andes because of the omnipresent risk of escapes. Fallow, axis and roe deer (Dama dama, Axis axis, Capreolus capreolus, respectively) also have been introduced to Chile and occur in many enclosures. Fallow deer recently escaped on Chiloé Island, became established and raised concerns because of its potential impacts on several endemic species on the island. The striking lack of information on feral deer may relate to policies and laws about firearms and restricted access to hunting areas, resulting in the apparent absence of popular hunting, which, nevertheless, could be a potential tool should the invasion continue and lead to future deer overabundance.

Huemul heresies: beliefs in search of supporting data. 2. Biological and ecological considerations

Scarce information from remnant huemul (Hippocamelus bisulcus) populations in marginal habitats can lead to erroneous interpretations of the species’ natural history, such as assumptions of being a highly inflexible species. We evaluated discrepancies between historical accounts and recent interpretations regarding biological and ecological traits to better understand factors preventing recovery of highly endangered huemul. Early information supports the theory that huemul are currently living under suboptimal conditions. We find variability to be the norm for huemul, as with other cervids, in regard to antler characteristics, group size and density, sexual segregation, and social and feeding behaviours. No evidence supports competition and disease from livestock or red deer as having caused declines or preventing recovery. Instead, livestock management, particularly presence of people and dogs, creates incompatibilities. Where red deer are sympatric with huemul, red deer are outnumbered by livestock by 2100%, and being regularly inspected at slaughter, livestock provide a good proxy for diseases afflicting red deer. Inadequate antipredator responses due to evolutionary absence of cursorial predators are unsupported as several Canis species coexisted with huemul, overlapping with dogs that arrived with Paleoindians. Three populations have increased despite high predator density. Age at maturity for huemul is 1 year, with evidence that fawns may also breed. Reported twinning needs confirmation, but occurs in congeneric taruca (H. antisensis) and other Odocoilines, and huemul frequently raise fawns successfully every year; life cycle calculations should apply these parameters. Like taruca, dominance group breeding systems have been described repeatedly. Although huemul bucks were recently claimed unique by displaying territoriality year-round, data do not support such behaviour. Two sole dispersal records (8 and 15.5 km) are unlikely to represent maximum dispersal capacity and do not support barriers assumed from few kilometres of unsuitable habitat. Huemul using 500 ha could predictably disperse up to 90 km, well within the ranges of other cervids. Mistakenly assuming barriers and underestimating reproductive capacity may distract from discovering the factors affecting recolonisations. Sustained recovery may depend on re-establishing source populations on more productive habitats, guided by zooarcheological and historical data.

Seasonal and specific diet variations in sympatric red and fallow deer of southern Spain: a preliminary approach to feeding behaviour

We studied the diet composition and diet overlap in sympatric red deer (Cervus elaphus hispanicus) and fallow deer (Dama dama) throughout a whole year in order to determine variation due to season, species, sex and age class by analysing rumen contents samples of 81 red and 69 fallow deer shot monthly during 2008–09 in Sierra de Andújar Natural Park, southern Spain. We assessed diet similarity and possible inter- and intra-specific foraging competition. We found different foraging strategies for both species and sexes during constraint periods, and several theoretical considerations of specific interactions and behaviour are discussed with respect to the Mediterranean environment. In both species an annual diet dominated by grasses was recorded, peaking in spring. Browses were an important food resource at the end of winter and at the end of summer, and fruit more in autumn and winter. Red deer ingested a higher proportion of browse than fallow deer, which consumed more acorns and for a longer time showed a better ability to compensate for nutritional constraint periods. An overall decline in diet similarity in summer and at the end of winter led us to assume that exploitative competition between red and fallow deer and even between sexes was probable. Red deer females showed low diet similarity to other deer, while there was a great diet overlap between red deer males and fallow deer females at the end of summer. Differences detected between both two species and sexes do not always support predictions deriving from specific body size and morpho-physiological characteristics, but can probably be explained as a consequence of different metabolic demands. The relationship between plant nutritional attributes and food selection according to reproductive or physiological status and seasonal demands for both sexes and species should be researched in order to perform a better assessment of deer feeding behaviour.