A Review of Cervidae Visual Ecology

This review examines the visual systems of cervids in relation to their ability to meet their ecological needs and how their visual systems are specialized for particular tasks. Cervidae encompasses a diverse group of mammals that serve as important ecological drivers within their ecosystems. Despite evidence of highly specialized visual systems, a large portion of cervid research ignores or fails to consider the realities of cervid vision as it relates to their ecology. Failure to account for an animal's visual ecology during research can lead to unintentional biases and uninformed conclusions regarding the decision making and behaviors for a species or population. Our review addresses core behaviors and their interrelationship with cervid visual characteristics. Historically, the study of cervid visual characteristics has been restricted to specific areas of inquiry such as color vision and contains limited integration into broader ecological and behavioral research. The purpose of our review is to bridge these gaps by offering a comprehensive review of cervid visual ecology that emphasizes the interplay between the visual adaptations of cervids and their interactions with habitats and other species. Ultimately, a better understanding of cervid visual ecology allows researchers to gain deeper insights into their behavior and ecology, providing critical information for conservation and management efforts.

Evaluation of a combined and portable light-ultrasound device with which to deter red deer

Human–wildlife conflicts are a growing problem in Northern Hemisphere where wild ungulates are one of the taxonomic groups most frequently involved. To mitigate these conflicts, it is essential to develop preventive actions able to avoid encounters between wildlife and human (activities). We here employed photo-trapping to evaluate the behaviour of red deer (Cervus elaphus) when confronted with dissuasive portable deterrents that function on the basis of changing patterns of light and ultrasound. This was done by following a before/after experimental design, with two phases: (i) a test phase, with active deterrents, and (ii) a control phase, without deterrents. When deterrents were activated they achieved a 48.96% reduction in the frequency of use by red deer (up to 66.64% when it was assessed on a thinner Sect. 10 m wide from the line of deterrents) and produced a reduction of 67.71% in the frequency of deterrent-line crossings. However, a habituation effect was detected since the use by red deer of the treatment area increased as time since treatment. These results indicate that these portable devices are effective as regards dissuading deer, mainly on short time scales. The deterrents tested here could be suitable for use at focal points for short periods or in combination with other methods to improve their effectiveness in vulnerability points. This device could potentially be used to mitigate conflicts caused by wildlife species and in response to relevant and timely situations, such as vehicle collisions and damage to crops, among others.

Wombat Roadkill Was Not Reduced by a Virtual Fence. Comment on Stannard et al. Can Virtual Fences Reduce Wombat Road Mortalities? Ecol. Eng. 2021, 172, 106414

The roadkill of wildlife is a global problem. Much has been written about deterring wildlife from roads, but, as of yet, there is no empirical support for deterrents based on visual and/or auditory signals. A recent paper entitled 'Can virtual fences reduce wombat road mortalities?'reported the results of a roadkill mitigation trial. The authors installed a 'virtual fence' system produced by iPTE Traffic Solutions Ltd. (Graz, Austria) and evaluated its effectiveness for reducing roadkills of bare-nosed wombats (Vombatus ursinus) in southern Australia. The authors recorded roadkills in a simple Before-After-Control-Impact design but did not conduct any formal statistical analysis. They also measured three contextual variables (vegetation, wombat burrows, and vehicle velocity) but did not link these to the occurrence of roadkills in space and time. The authors concluded that the iPTE virtual fence system was 'minimally effective', yet 'appears promising'. Our analysis of their data, using standard inferential statistics, showed no effect of the virtual fence on roadkills whatsoever. We conclude that the iPTE system was not effective for mitigating the roadkills of bare-nosed wombats.

A test of wildlife warning reflectors as a way to reduce risk of wildlife-train collisions

Looking for an effective method to reduce risk of animal-train collisions, we tested the system of wildlife warning reflectors, a method usually used on roads. The research was conducted in central Poland, along a 2.1 km stretch of the E65 railway line near Warsaw, during eight months, in the years 2010–2011. For six months of a test period, the reflectors were uncovered (active) and, for the next two months of the control period, they were covered (non-active). Digital cameras were used to register animal reactions to trains 24-hours per day. We compared the probability of escape (escape = 1; no reaction = 0) from an oncoming train during test and control periods of the research, in different parts of a day (i.e. day vs. night) and compared escape time of roe deer between day and night and with reflectors covered and uncovered. Roe deer (Capreolus capreolus), red fox (Vulpes vulpes) and brown hare (Lepus europaeus) were observed most often (702 observations in total). The status of reflectors (covered/uncovered) did not influence the probability of animals’ escape from an oncoming train. The only factors that affected the probability of escape were animal species and time of a day. Of the three species, roe deer was most likely to escape from an oncoming train (89% of probability at day and 52% during night, pooled data for covered and uncovered reflectors). Timing of roe deer escape from an oncoming train did not differ between day (6.4 seconds) and night, with either reflectors covered (7.5 seconds) or uncovered (4.6 seconds). The results indicated that wildlife warning reflectors were not effective to modify animal behaviour and to reduce risk of animal-train collisions.

Roadkill mitigation is paved with good intentions: a critique of Fox et al. (2019)

In a recent publication, Fox et al. (2019) described a three-year trial of a ‘virtual fence’ installed to reduce wildlife roadkills in north-eastern Tasmania. The authors reported a 50% reduction in total roadkills, concluding that the ‘virtual fence’ had the potential to substantially reduce roadkill rates. The field of roadkill mitigation has a long history of promising techniques that are ultimately found wanting, so we evaluated the conceptual basis of the ‘virtual fence’ and the design and analysis of the trial. Of the two stimuli emitted by the ‘virtual fence’, its lights only partly match the sensory capabilities of the target species, its sound frequency is suitable but the intensity is unknown, and both stimuli are artificial and lack biological significance, so will be prone to habituation once novelty wanes. The trial, conducted in three phases, revealed a total of eight methodological flaws ranging from imprecise measurements, confounding effects of treatments, low statistical power, violation of test assumptions and failure to consider habituation. Greater caution is needed in interpreting the findings of this study, and well designed, long-term trials are required to properly assess the ‘virtual fence’.

Virtual fence devices – a promising innovation: a response to Coulson and Bender (2019)

Coulson and Bender (2019) have provided a critique to our paper ‘Roadkill mitigation: trialing virtual fence devices on the west coast of Tasmania’ (Fox et al. 2019). Here, we clarify some ambiguous points that have confused Coulson and Bender and refute other claims. Although we presented results from a single study and a trial, we stand by our claim that these devices hold great promise and are worthy of further research.

Effects of reflective warning markers on wildlife

Light pollution has become one of the top issues in environmental pollution, especially concerning how secondary light pollution, such as from traffic reflective materials, influences animal distribution and behavior. In this study, 15 camera traps were set up at sites with or without reflective warning markers (RWM) in coniferous forests on Cangshan Mountain located in Dali Prefecture, China. The results showed that the number of independent photographs and species at sites without RWMs were significantly higher than those at sites with RWMs. Significant differences were found between daytime and nighttime composition of bird species and non-flying mammals between two sites. This study found that RWMs had negative effects on wildlife, with the avoidance response of birds to RWMs being more obvious than that of animals at daytime. It is recommended that the use of reflective materials be carefully considered, especially in protected areas.

Wildlife warning reflectors do not mitigate wildlife-vehicle collisions on roads

Wildlife-vehicle collisions cause human fatalities and enormous economic and ecological losses on roads worldwide. A variety of mitigation measures have been developed over the past decades to separate traffic and wildlife, warn humans, or prevent wildlife from entering a road while vehicles are passing by, but only few are economical enough to be applied comprehensively. One such measure, wildlife warning reflectors, has been implemented over the past five decades. However, their efficacy is questioned because of contradictory study results and the variety of applied study designs and reflector models. We used a prospective, randomized non-superiority cross-over study design to test our hypothesis of the inefficacy of modern wildlife warning reflectors. We analyzed wildlife-vehicle collisions on 151 testing sites of approximately 2 km in length each. During the 24-month study period, 1984 wildlife-vehicle collisions were recorded. Confirmatory primary and exploratory secondary analyses using a log-link Poisson mixed model with normal nested random intercepts of observation year in road segment, involved species, and variables of the road segment and the surrounding environment showed that reflectors did not lower the number of wildlife-vehicle collisions by a relevant amount. In addition, variables of the road segment and the surrounding environment did not indicate differential effects of wildlife warning reflectors. Based on our results, we conclude that wildlife warning reflectors are not an effective tool for mitigating wildlife-vehicle collisions on roads.