Aksel Bo Madsen

Genetic consequences of population decline in the European otter (Lutra lutra): an assessment of microsatellite DNA variation in Danish otters from 1883 to 1993

The European otter (Lutra lutra) was common in Denmark until the 1960s, but its present distribution encompasses only a minor part of the country. The aim of this study was to assess whether the recent population decline has resulted in loss of genetic variability and to gain further insight into the dynamics of the population decline. This was done by analysing microsatellite DNA variation in contemporary and historical samples, the latter encompassing DNA samples extracted from museum specimens covering a time–span from the 1880s to the 1960s. Tests for differences in expected heterozygosity and the numbers of alleles in contemporary versus historical samples and a test for detecting population bottlenecks provided few indications of a recent bottleneck and loss of variability. However, a procedure for detecting population expansions and declines, based on the genealogical history of microsatellite alleles, suggested that a drastic long–term population decline has taken place, which could have started more than 2000 years ago, possibly due to ancient anthropogenic pressure. Finally, assignment tests and pairwise FST values suggested weak but statistically significant genetic differentiation between the extant population and historical samples of otters from other regions in Denmark, more likely reflecting differentiation among original populations rather than recent drift.

Effectiveness of Wildlife Warning Reflectors in Reducing Deer-Vehicle Collisions: A Behavioral Study

Various reflector systems have been in use for a number of years to reduce deer-vehicle collisions, but their effectiveness on a long-term basis is still in question. We examined habituation of deer to repeatedly occurring light reflections from WEGU reflectors by studying the behavioral responses of fallow deer (Dama dama). Our experimental design eliminated factors normally associated with light reflections from reflectors (vehicle noise, light), and deer were exposed to light reflections at predetermined time intervals. The distribution of the behaviors flight, alarm, movement of head, and no reaction varied among nights. Despite this variability, however, fallow deer exhibited increasing indifference to reflections, which was explained by a habituation to the stimulus. Our results are expected to be valid for other species of deer and other types of reflectors. Habituation of deer and technical limitations of the reflectors, such as limited angle and low light intensity of the reflection, mean that reflectors are not reliable as a method to reduce the number of deer-vehicle accidents on a long-term basis.

Factors causing traffic killings of roe deer Capreolus capreolus in Denmark

In Europe, roe deer Capreolus capreolus is one of the biggest mammal species killed in traffic, and the number of accidents seems to increase. The purpose of our paper is to point out the most important factors causing traffic killings and to suggest conservation measures that may reduce the number of roe deer killings in traffic. Our study is based on data including 115 roe deer killed in traffic at the Kalø estate in East Jutland, Denmark, during 1956–1985. No significant correlation was found between the number of traffic killings of roe deer and mean daily traffic, but the number of roe deer killed in traffic varied significantly over the seasons. The distribution pattern of roe deer/car collision sites was clumped. The risk of being killed in traffic was highest for young and old roe deer. Significantly more adult females, adult males and subadult males than expected were killed in traffic, and significantly more individuals were killed in years when most of the fields next to the roads were left unsown in winter. We suggest that the following measures be taken to prevent traffic killings: increasing areas with winter cereal or wintergreen fields, clearing the vegetation adjacent to roads and reducing car speed in high-risk areas.

Habitat factors and the presence or absence of otters Lutra lutra in Denmark

The purpose of the present study was to examine the relative influence of different habitat factors on ottersLutra lutra (Linnaeus, 1758) and to develop a predictive model to better understand the distribution of the otter in Denmark. During the National Otter Survey in 1991 data were collected on 19 variables which reflected aspects of habitat structure, composition, organic pollution and human disturbance. Multiple logistic regression analysis was used to estimate probabilities of the presence of otters as a function of one or more explanatory variables. Six variables (county, pH, water depth, presence of trees, bottom substrate and Saprobien-Index) were identified. In Denmark, otter habitat typically consists of water courses with depths > 1 m over a varied bottom, with pH > 7.0, Saprobien-Index on II–III to III (indicating slight organic pollution) with no trees on the banks. Some of these variables reflect highly productive waters. The use of the otter as an indicator of good water quality and/or aquatic habitat should be used with care.

Diet of free-ranging American mink and European polecat in Denmark

Stomach and intestine contents of 211 American minkMustela vison Schreber, 1777 from two areas (Thy and Bornholm) in Denmark and stomach contents of 47 polecatsM. putorius Linnaeus, 1758 from Thy were analysed. Sympatric mink (from Thy) preyed mostly on mammals (55% occurrence), followed by amphibians (36%), birds (33%) and fish (30%), whereas polecat preyed mostly on amphibians (87%) and mammals (34%), and only occasionally on birds (9%) and fish (6%). Allopatric mink (from Bornholm) preyed mostly on birds (50%), followed by mammals (42%), fish (25%) and amphibians (4%). With the possible exception of some amphibians, no endangered species were found in their diet. No differences were found in food composition between wild and escaped farm mink. The concern that mink in general might have a detrimental effect on its prey species and other mustelids in terms of food competition in Denmark may be unjustified. It cannot be ruled out, however, that mink may locally have a seriously negative effect on some specific prey species, and clearly, more data is needed on eg prey abundance and spring and summer mink diet, to make stronger conclusions.

Genetic differentiation of foxes (Vulpes vulpes) analysed by means of craniometry and isozymes

Abstract In 1997–1999, 411 red foxes Vulpes vulpes were collected from all over Denmark. Among these 205 were used for a univariate craniometrical investigation on six skull traits. 308 of the foxes were analysed by horizontal starch gel electrophoresis. Of the studied 18 enzymes, 14 were monomorphic and four polymorphic. Of the latter ones three were used for further analysis, as one enzyme system was difficult to score. No genetic heterogeneity within samples between sexes was revealed. However both genetic and morphometrical differentiation were found between the regions, with the foxes from Copenhagen significantly deviating from all other samples, including those from the remaining part of Zealand. Thus, our data suggest that the foxes from Copenhagen may be considered as an isolated population with limited amount of gene flow with the other populations in Denmark. Possible causes of such limited gene flow are discussed.

Present and past microsatellite variation and assessment of genetic structure in Eurasian badger (Meles meles) in Denmark

During the past 50 years the number of badgers (Meles meles) in Denmark has declined by c. 50%. To assess the genetic consequences of the demographic decline, six DNA-microsatellite loci were used to analyse 139 badger tissue-samples, which were collected in 1995–98 from three zones (1, 2 and 3) in Jutland (Denmark). Results from contemporary samples were compared to data obtained from DNA extracted from teeth belonging to 39 badgers collected from zones 1 and 2 in 1957–66. The microsatellites showed a low to moderate polymorphism, and the within area genetic diversity (H E) was relatively low (0.308 ≤H E ≤ 0.441) as compared to other carnivores and mustelids. Genetic differentiation among the three recent sampling zones was significant (FST = 0.072,P 0.05). Despite the drastic recent decline, Danish badgers did not show apparent signs of genetic bottlenecks in both recent and historical samples. The use of molecular techniques which allowed us to work with small amounts of degraded DNA extracted from old teeth, allowed us to exclude the hypothesis that genetic differentiation between zones 1 and 2 was owing to a barrier, which has appeared in the last 50 years. Furthermore, the low genetic variability and therefore the relatively high genetic differentiation shown by Danish badgers were also shown not to be the result of the recent drastic population decline.

Effectiveness of Acoustic Road Markings in Reducing deer-vehicle Collisions: A Behavioural Study

The behavioural responses and habituation of fallow deer Dama dama to play-back sounds from repeatedly occurring acoustic road markings were studied during 13 nights. Our experimental design eliminated factors normally associated with passing vehicles (e.g. vehicle noise and light), and fallow deer were exposed to play-back sounds from road markings at predetermined time intervals. Though the distribution of the predefined behavioural responses ‘flight’, ‘alarm’, ‘movement of head’ and ‘no reaction’ varied among nights, the fallow deer exhibited increasing indifference to sounds from road markings with time, and this we explained as being habituation to the acoustic stimulus. As we expect our results to be valid for other species of deer as well, we find that acoustic road markings are not a reliable method to reduce the number of deer-vehicle collisions on a long-term basis.

Effectiveness of odour repellents on red deer (Cervus elaphus) and roe deer (Capreolus capreolus): a field test

Chemical repellents are promoted as a method to reduce ungulate–vehicle collisions and ungulate browsing damages to agricultural and forestry resources. We tested the effectiveness of two odour repellents (Mota FL and Wolf Urine) on the foraging behaviour and area avoidance of free-ranging roe deer (Capreolus capreolus) and red deer (Cervus elaphus). The effects of the repellents were assessed by comparing deer visitation rates to sand arenas before and after application of repellents and visitation rates to control arenas. Neither of the tested products reduced deer visitation rates. Rapid habituation to olfactory stimuli and lack of sensitivity to predator odours may explain the ineffectiveness of the repellents to alter the behaviour of the deer. The results indicate that the tested products have no effects on roe deer and red deer behaviour and suggest that the effectiveness of the chemical area repellents as a measure to reduce deer–vehicle collision risk and browsing damages is questionable.

Mortality and reproductive patterns of wild European polecatsMustela putorius in Denmark

Despite its relative abundance and wide geographical range, the population dynamics and reproductive biology of the European polecatMustela putorius Linnaeus, 1758 are largely unknown as to the wild living. We therefore investigated age and reproductive status of 239 Danish polecats primarily killed in traffic or trapped during 1998–2004. Males comprised two third of all individuals in all age groups. Based on a static life table, apparent annual mortality was 68% during the first year of life, 33% during the second year and 65% from the third year in both sexes. The mean (± SE) litter size of 5.95 ± 0.62 (n = 18), estimated from placental scar counts, was significantly lower than litter sizes at birth reported for captive individuals but consistent with litter sizes reported for wild polecats in Russia. Female yearlings conceived at the same rate and produced litters of the same size as older individuals.Males had spermatozoa in their testes from February through August. Testes mass peaked in April and May, ie the same period when most females conceive. A lower prevalence of individuals with spermatozoa in yearlings suggests that most males postponed sexual maturity to two years of age.