Deer Behavior Affects Density Estimates With Camera Traps, but Is Outweighed by Spatial Variability

Henrich, Maik; Härtig, Florian; Dormann, Carsten F.; Kühl, Hjalmar S.; Peters, Wibke; Franke, Frederik; Peterka, Tomas; Šustr, Pavel; Heurich, Marco

doi:10.3389/fevo.2022.881502

Cited by 14 publications

(23 citation statements)

References 86 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In our study area, traditional count-based methods are the standard method to obtain abundance indices, which are often unable to capture the sampling process 78 , 79 . A recent study by 80 used camera trap-based random encounter models and distance sampling to estimate red deer density during the same study period in part of our study area, the Bavarian Forest National Park and part of Šumava National Park (Fig. 1 ).…”

Section: Discussionmentioning

confidence: 99%

Spatial variation in red deer density in a transboundary forest ecosystem

Tourani

Franke

Heurich

et al. 2023

Sci Rep

Self Cite

View full text Add to dashboard Cite

Forests in Europe are exposed to increasingly frequent and severe disturbances. The resulting changes in the structure and composition of forests can have profound consequences for the wildlife inhabiting them. Moreover, wildlife populations in Europe are often subjected to differential management regimes as they regularly extend across multiple national and administrative borders. The red deer Cervus elaphus population in the Bohemian Forest Ecosystem, straddling the Czech-German border, has experienced forest disturbances, primarily caused by windfalls and bark beetle Ips typographus outbreaks during the past decades. To adapt local management strategies to the changing environmental conditions and to coordinate them across the international border, reliable estimates of red deer density and abundance are highly sought-after by policymakers, wildlife managers, and stakeholders. Covering a 1081-km2 study area, we conducted a transnational non-invasive DNA sampling study in 2018 that yielded 1578 genotyped DNA samples from 1120 individual red deer. Using spatial capture-recapture models, we estimated total and jurisdiction-specific abundance of red deer throughout the ecosystem and quantified the role of forest disturbance and differential management strategies in shaping spatial heterogeneity in red deer density. We hypothesised that (a) forest disturbances provide favourable habitat conditions (e.g., forage and cover), and (b) contrasting red deer management regimes in different jurisdictions create a differential risk landscape, ultimately shaping density distributions. Overall, we estimated that 2851 red deer (95% Credible Interval = 2609–3119) resided in the study area during the sampling period, with a relatively even overall sex ratio (1406 females, 95% CI = 1229–1612 and 1445 males, 95% CI = 1288–1626). The average red deer density was higher in Czechia (3.5 km−2, 95% CI = 1.2–12.3) compared to Germany (2 km−2, 95% CI = 0.2–11). The effect of forest disturbances on red deer density was context-dependent. Forest disturbances had a positive effect on red deer density at higher elevations and a negative effect at lower elevations, which could be explained by partial migration and its drivers in this population. Density of red deer was generally higher in management units where hunting is prohibited. In addition, we found that sex ratios differed between administrative units and were more balanced in the non-intervention zones. Our results show that the effect of forest disturbances on wild ungulates is modulated by additional factors, such as elevation and ungulate management practices. Overall density patterns and sex ratios suggested strong gradients in density between administrative units. With climate change increasing the severity and frequency of forest disturbances, population-level monitoring and management are becoming increasingly important, especially for wide-ranging species as both wildlife and global change transcend administrative boundaries.

show abstract

Section: Discussionmentioning

confidence: 99%

Spatial variation in red deer density in a transboundary forest ecosystem

Tourani

Franke

Heurich

et al. 2023

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…The necessity of accounting for behavioral heterogeneity across individuals has received increasing attention in the conservation literature (Merrick & Koprowski, 2017; Kelleher, Silla & Byrne, 2018; Henrich et al ., 2022). Behavioral variability can considerably impact conservation effectiveness in a number of ways, from its impact upon individual fitness, to how it affects the suitability of conservation action across contexts and populations.…”

Section: Discussionmentioning

confidence: 99%

Failure to account for behavioral variability significantly compromises accuracy in indirect population monitoring

Wessling

Surbeck

2022

Animal Conservation

View full text Add to dashboard Cite

Indirect wildlife population surveying largely depends upon counts of artifacts of behavior (e.g., nests or dung). Likelihood to encounter these artifacts is derived from both artifact production and decay, and variability in production behavior is considered to contribute minimally to inaccuracy in wildlife estimation. Here, we demonstrate how ignoring behavioral variability leads to significant population misestimation, using an example of an endangered ape, the bonobo (Pan paniscus). Until now, a single estimate of nest construction rate has been used to extrapolate bonobo densities, assumed to be broadly representative of bonobo sign production behavior. We estimated nest construction rates across seasons and social groups at the Kokolopori Bonobo Reserve, Democratic Republic of the Congo, and find nest construction rates in bonobos to be highly variable across populations as well as seasonal within populations. Failure to account for this variability led to degradation in the accuracy of bonobo population density estimates, accounting for a likely overestimation of bonobo numbers by 34%, and at worst as high as 80%. With this example, we demonstrate that failure to account for inter-and intrapopulation behavioral variation compromises the ability to estimate both relative and absolute wildlife abundances. We argue that variation in sign production is but one of the several potential ways that behavioral variability can affect conservation monitoring, should be measured across contexts whenever possible, and must be considered in population estimation confidence intervals. With increasing attention to behavioral variability as a potential tool for conservation, conservationists must also account for the impact that behavioral variability can have upon wildlife population estimation. Our results underline the importance of observational research to wildlife monitoring schemes as a critical component of conservation management. We discuss the avenues through which behavioral variability is likely to impact wildlife monitoring accuracy and precision and propose potential approaches for accounting for behavioral variability in wildlife monitoring.

show abstract

“…We estimated sex ratio based on independent detections of female and male roe deer as done in previous studies (Heurich et al 2016, Henrich et al 2022). Detection probability of roe deer could vary across sex, seasons, years, and sites, which could introduce a bias in the sex ratio estimation.…”

Section: Discussionmentioning

confidence: 99%