Comparison of spotlighting monitoring data of European brown hare (Lepus europaeus) relative population densities with infrared thermography in agricultural landscapes in Northern Germany.

A successful wildlife management requires monitoring. Including non-scientific volunteers into monitoring actions is a common way for obtaining long-term and comprehensive data. Hunters present a valuable target group as they are spread out nationwide in Germany and additionally, they provide a know-how regarding game species. Since 1990s, various German hunting associations established monitoring programs and motivated hunters to join, in order to record population sizes of huntable game species under standardized census methods. The aim of this study was to compare instructed hunters performed spotlight counts of European brown hares with thermography in three federal states (Lower-Saxony, Saxony-Anhalt, North Rhine-Westphalia) in 2015-2018 in Northern Germany. Therefore, we modelled the number of hares counted by both methods with the associated observed area. Moreover, we performed repeated thermographic counts in selected areas and performed distance sampling to test the deviations of estimated population densities within a short time period. Repeated infrared thermographic counts on three consecutive nights show a coefficient of variation from 6.6% to 15.5% with deviations of 2.2-2.7 hares per 100 ha, while the method of distance sampling reveals minor deviations of 0.9-1.7 hares per 100 ha and a coefficient of variation from 3.1-7.4%. The coefficient of variation value between spotlight and infrared thermographic count lies between 0 to 21.4%. Our model confirmed no significant differences between the European brown hare density estimations based on a spotlight count and an infrared thermographic count on the following night. The results provide insight into the dimension of the error margin of density estimations performed by spotlight counts. Therefore, we recommend to take possible counting errors into account and to ideally perform repeated counts to assess the error margin for each counting site. This would help for example to quantify the uncertainty in the calculation of mortality rates. Additionally, our results show that monitoring data generated by instructed hunters can provide reliable and valid data, if implemented and conducted in a standardized scientific way.

Relationship between heavy metal accumulation and morphometric parameters in European hare (Lepus europaeus) inhabiting various types of landscapes in southern Poland.

To evaluate the influence of hazardous substances in the environment, studies of pollutant accumulation in wild living animals are needed. Studies dealing with heavy metal contamination in mammals usually focus on a single organ. We investigated accumulation of heavy metals as well as iron in European hare (Lepus europaeus) living in southern Poland, Malopolska Province. Hares were captured during the hunting season. We tested metal accumulation in 14 organs and tissues using 35 individuals with known body weight and sex inhabiting agricultural, industrial and other types of landscapes. To obtain deeper insight into contamination patterns, we used accumulation data from the liver since it is the most frequently investigated organ and prone to pollution accumulation. Based on the data obtained for the liver, we tested the impact of metal pollution on hare morphology, including body length and several skull cranimetric parameters. Metals content differed between organs. Moreover, individuals from industrial areas had higher Cd content in their body. We distinguished two groups of elements: the first group, Cd, Fe and Zn, revealed the highest toxic effect in the liver and kidneys; the second group, Cr, Ni, and Pb, accumulated primarily in the brain. Hares inhabiting industrial areas had higher concentration of Cd and Pb, and lower levels of Cr and Fe in their liver in comparison with those from agricultural and forest habitats. Heavy metals had an effect on body length that was negatively associated with Cr levels. Skull diastema length was associated positively with accumulation of Cd and Pb. We showed that hare organs and tissues could be used as bioindicators of environmental pollution by heavy metals.

Conservation considerations for a management measure: an integrated approach to hare rearing and release.

Wildlife managers are challenged with the task of deciding whether a management measure is appropriate or not, and furthermore they have to convince others about the merits of their decision. Population decline of some hare species (genus Lepus) has resulted in their Red Listing and conservation measures are being undertaken. Release or restocking is a frequent measure in some countries, and thousands of hares are released annually, mainly for hunting purposes. These hares can be obtained by either intensive or extensive rearing or translocation of the wild animals. Each method entails difficulties and different survival rates in the wild. Survival rates in the wild are low for hares intensively reared in cages but are higher for hares reared extensively in enclosures and wild translocated hares. The benefits of the hare release practice are significantly lower than the action's implementation cost. Hare releases have not increased significantly the wild hare population or the hunting harvest in areas where the practice has been applied. The risk of genetic and evolutionary degradation and pathogen transmission is possible in wild populations. The need for wise management of this practice is evident and the term 'Permitted Transferring Units' should be introduced to denote regions where hares should not be transferred for rearing and release.

Modeling the dynamics of woody plant-herbivore interactions with age-dependent toxicity.

In this paper we study the effects that woody plant chemical defenses may have on interactions between boreal hares that in winter feed almost entirely on twigs. We focus particularly on the fact that toxin concentration often varies with the age of twig segments. The model incorporates the fact that the woody internodes of the youngest segments of the twigs of the deciduous angiosperm species that these hares prefer to eat are more defended by toxins than the woody internodes of the older segments that subtend and support the younger segments. Thus, the per capita daily intake of the biomass of the older segments of twigs by hares is much higher than their intake of the biomass of the younger segments of twigs. This age-dependent toxicity of twig segments is modeled using age-structured model equations which are reduced to a system of delay differential equations involving multiple delays in the woody plant-hare dynamics. A novel aspect of the modeling was that it had to account for mortality of non-consumed younger twig segment biomass when older twig biomass was bitten off and consumed. Basic mathematical properties of the model are established together with upper and lower bounds on the solutions. Necessary and sufficient conditions are found for the linear stability of the equilibrium in which the hare is extinct, and sufficient conditions are found for the global stability of this equilibrium. Numerical simulations confirmed the analytical results and demonstrated the existence of limit cycles over ranges of parameters reasonable for hares browsing on woody vegetation in boreal ecosystems. This showed that age dependence in plant chemical defenses has the capacity to cause hare-plant population cycles, a new result.

Pattern-oriented modelling: a 'multi-scope' for predictive systems ecology.

Modern ecology recognizes that modelling systems across scales and at multiple levels-especially to link population and ecosystem dynamics to individual adaptive behaviour-is essential for making the science predictive. 'Pattern-oriented modelling' (POM) is a strategy for doing just this. POM is the multi-criteria design, selection and calibration of models of complex systems. POM starts with identifying a set of patterns observed at multiple scales and levels that characterize a system with respect to the particular problem being modelled; a model from which the patterns emerge should contain the right mechanisms to address the problem. These patterns are then used to (i) determine what scales, entities, variables and processes the model needs, (ii) test and select submodels to represent key low-level processes such as adaptive behaviour, and (iii) find useful parameter values during calibration. Patterns are already often used in these ways, but a mini-review of applications of POM confirms that making the selection and use of patterns more explicit and rigorous can facilitate the development of models with the right level of complexity to understand ecological systems and predict their response to novel conditions.

Is the large size of the pinna of the ear of the European hare (Lepus europaeus) due to its role in thermoregulation or in anterior capital shock absorption?

Large pinnae are characteristic of the Leporids, and the pinna is known to have a thermoregulatory role. Another role has been hypothesized for the pinna of Lepus spp., as a part of a suspensory system for the greater portion of the head, absorbing shock that might otherwise interfere with vision during high-speed locomotion. We compared the lengths of the pinnae of adult European hares Lepus europaeus from the source population in the cooler climate of England with those of the introduced population in the warmer climate of Australia, and we compared the lengths of the pinnae of hares that had grown in cooler weather with those that had grown in warmer weather. There were no significant differences between each of the comparisons, indicating that the size of the pinna is not determined by thermoregulatory requirements at rest. We compared the growth in length of the pinnae and the legs with growth in body mass, and growth in the mass of the pinnae with the masses of the head and the eyeballs, and found support for the suspension hypothesis. We suggest that the rapid growth of the pinna is because visual acuity is a function of absolute eye size, not relative eye size, yet juvenile hares are subject to the same predator pressure as adult hares, and equally need to maximize visual acuity while running at high speeds in dim light. We believe that the large size of the pinna is determined by its role in anterior capital suspension, not in thermoregulation.

Peak energy turnover in lactating European hares: the role of fat reserves.

European hares (Lepus europaeus) in central Europe have high energetic costs of reproduction, mainly due to precocial, rapidly growing young that rely largely on energy-rich milk. Thus, hares in this climate build up large fat stores during winter that are then gradually depleted during the spring-to-autumn breeding season. We hypothesized that the diminishing fat stores of females over the breeding season might affect resource allocation, peak energy assimilation during lactation or the total investment in offspring. Therefore, we measured energy intake, milk quality and milk production throughout lactation in spring, summer and autumn in females raising (size-manipulated) litters with three young each, under a natural photoperiod but at buffered ambient temperatures inside our facility. Over the course of the breeding season, the amount of milk production remained constant, but the fat content of the milk decreased. Hence, total energy transfer to young decreased significantly in autumn. By using undecanoic acid as a tracer of body fat mobilization, we were able to show that milk fat partially originated from maternal fat stores, particularly in spring. The peak sustained energy assimilation rates of lactating females were significantly higher in autumn, due to increased rates of food intake. We conclude that fat stores allow female hares to downregulate energy intake and expenditure early in the breeding season, whereas late breeding forces them to reach peak energy intake levels. Accordingly, we suggest that in hares, peak energy turnover during lactation varies with the availability of fat reserves. Limits to the sustained metabolic rate serve as variable constraints on reproductive investment. Thus, there might be a trade-off in energetic costs to mothers rearing early versus late litters in the year.

Unstable dynamics and population limitation in mountain hares.

The regular large-scale population fluctuations that characterize many species of northern vertebrates have fascinated ecologists since the time of Charles Elton. There is still, however, no clear consensus on what drives these fluctuations. Throughout their circumpolar distribution, mountain hares Lepus timidus show regular and at times dramatic changes in density. There are distinct differences in the nature, amplitude and periodicity of these fluctuations between regions and the reasons for these population fluctuations and the geographic differences remain largely unknown. In this review we synthesize knowledge on the factors that limit or regulate mountain hare populations across their range in an attempt to identify the drivers of unstable dynamics. Current knowledge of mountain hare population dynamics indicates that trophic interactions--either predator-prey or host-parasite--appear to be the major factor limiting populations and these interactions may contribute to the observed unstable dynamics. There is correlative and experimental evidence that some mountain hare populations in Fennoscandia are limited by predation and that predation may link hare and grouse cycles to microtine cycles. Predation is unlikely to be important in mountain hare populations in Scotland as most hares occur on sporting estates where predators are controlled, but this hypothesis remains to be experimentally tested. There is, however, emerging experimental evidence that some Scottish mountain hare populations are limited by parasites and that host-parasite interactions contribute to unstable dynamics. By contrast, there is little evidence from Fennoscandia that parasitism is of any importance to mountain hare population dynamics, although disease may cause periodic declines. Although severe weather and food limitation may interact to cause periodic high winter mortality there is little evidence that food availability limits mountain hare populations. There is a paucity of information concerning the factors limiting or regulating mountain hare populations in the Alps of Central Europe or in the tundra and taiga belts of Russia. Future research on mountain hare population dynamics should focus on the interactions between predation, parasitism and nutrition with stochastic factors such as climate and anthropogenic management including harvesting.

Long-term patterns in European brown hare population dynamics in Denmark: effects of agriculture, predation and climate.

BACKGROUND: In Denmark and many other European countries, harvest records suggest a marked decline in European brown hare numbers, a decline often attributed to the agricultural practice. In the present study, we analyse the association between agricultural land-use, predator abundance and winter severity on the number of European brown hares harvested in Denmark in the years 1955 through 2000. RESULTS: Winter cereals had a significant negative association with European brown hare numbers. In contrast to this, root crop area was positively related to their numbers. Remaining crop categories were not significantly associated with the European brown hare numbers, though grass out of rotation tended to be positively related. The areas of root crop production and of grass out of rotation have been reduced by approximately 80% and 50%, respectively, while the area of winter cereals has increased markedly (>70%). However, European brown hare numbers were primarily negatively associated with the number of red fox. Finally, we also found a positive association between mild winters and European brown hare numbers. CONCLUSION: The decline of Danish European brown hare populations can mainly be attributed to predation by red fox, but the development in agricultural land-use during the last 45 years have also affected the European brown hare numbers negatively. Additionally, though mild winters were beneficial to European brown hares, the increasing frequency of mild winters during the study period was insufficient to reverse the negative population trend.