Peter Sunde

Tolerance to humans of resting lynxes Lynx lynx in a hunted population

The tolerance of lynxes Lynx lynx to human presence and disturbance in a hunted population in Norway was studied using telemetry. Forest land within 200 metres from the nearest road or house was avoided by lynxes when resting (P < 0.01). The tolerance distance of resting lynxes towards intruding people was short (median 50 m), though strongly correlated with the horizontal vegetation cover (partial correlation, P < 0.02) and forest maturation stage (partial correlation, P < 0.02), but not with terrain inclination (partial correlation, P > 0.3). The lynxes did not enter steeper country (P > 0.4) or alter their daily walking distance (P > 0.7) after being disturbed. The data indicate that lynxes, even when suffering extensive, man-induced mortality, may tolerate high human activity within their range as long as sufficient stands of undisturbed, mature forest with dense horizontal cover are present.

Mortality of semi-domestic reindeer Rangifer tarandus in central Norway

During the last decade, losses of semi-domestic reindeer Rangifer tarandus have increased in central Norway. Natural mortality in a semi-domestic reindeer herd was studied by use of mortality sensing transmitters. From 15 April 1995 to 15 April 1996,135 of 612 animals equipped with radio collars were found dead. Adult females (>2 years old) suffered a mortality of 18.3%, of which 40.5% was due to predation. Yearlings suffered a yearly mortality of 20.2% of which 66.7% was due to predation. Calf mortality from 6 August 1995 to 15 April 1996 was 31.0%, of which 75.3% was due to predation. Predation by Eurasian lynx Lynx lynx was the predominant cause of death, with 39.3% of the total mortality. Accidents were the second most important cause of death, with 16.0% of the total mortality. Peaks in mortality were registered in September, November and January.

Behavioural Responses of GPS-Collared Female Red Deer Cervus elaphus to Driven Hunts

Precise knowledge of how game species react to different hunting practices is a prerequisite for sound management of intensively hunted populations. We compared behavioural and spatial behaviour of five GPS-collared female red deer Cervus elaphus in Denmark before, during and after exposure to 21 driven hunts (2–5 times each). In 53% of all hunts, deer left their normal home ranges within 24 hours, moving on average 4 km and remaining away for an average of six days. Compared to pre-hunt values, deer moved longer distances per unit time on the day of the hunt and during the following two nights. Diurnal activity (based on motion sensors) did not increase significantly on the hunting day, but was lower than normal the day after the hunt. Nocturnal activity was equal before and after hunts. Deer spent 96% of their time in (safer) forest habitats by day and 43% by night before and after hunts. No induced responses were conditional on distance to the hunters (0–1.5 km), hunt duration (1.3–6.4 hours) or the time elapsed since previous hunts (4 to >30 days). The inclination of deer to flee from areas following hunts might complicate attempts to optimise harvesting policies in landscapes with many landowners within a typical flight range.

Using counts of begging young to estimate post-fledging survival in Tawny Owls Strix aluco

Capsule The method reliably accounted for variation in brood size when used by a ‘naive’ observer.

How does harvest size vary with hunting season length

Manipulating hunting season length is often used as a population management tool but the effects of these changes on total harvest have rarely been studied. We modelled relative changes in national annual bag size as a function of relative change in hunting season length in 63 cases involving 28 species in Denmark (1957–2007). The duration of the hunting season, initially lasting 30–365 days, was modified to 39–204% of the former length. The undifferentiated effect of season length change on bag size change (all 63 cases) was not statistically significant (b = 0.16, 95%CI: -0.04–0.36), with a 10% (95%CI: -3–22%) predicted decrease in bag size upon a 50% reduction of season length. However, the functional relationship between the relative change in bag size and the change in season length differed between sedentary and non-sedentary species and interacted with the motivation behind changing season length (population management/ethical/other). In non-sedentary species, changes in bag size correlated positively with changes in season length (overall response: b = 0.54, 95%CI: 0.14–0.95): reducing the hunting season to 50% of its initial length would on average result in a 31% reduction (95% CI: 9–48%) of total bag size. This overall effect interacted with the motivation for season length changes, being strongest for ‘other reasons’ (mainly harmonization of hunting periods for related species) but was absent when seasons were changed for reasons of ‘population management’. In sedentary species, changes in season length had no effect on bag size. Our results suggest that manipulating hunting seasons of duration ≥ 1 month by less than 50% is generally inefficient as a means of predictably changing harvest rates. This may be because recreational hunters either invest a fixed effort or aim for a specific yield within a given season, neither strategy being affected by changes in hunting seasons.

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.

Weather conditions drive dynamic habitat selection in a generalist predator.

Despite the dynamic nature of habitat selection, temporal variation as arising from factors such as weather are rarely quantified in species-habitat relationships. We analysed habitat use and selection (use/availability) of foraging, radio-tagged little owls (Athene noctua), a nocturnal, year-round resident generalist predator, to see how this varied as a function of weather, season and availability. Use of the two most frequently used land cover types, gardens/buildings and cultivated fields varied more than 3-fold as a simple function of season and weather through linear effects of wind and quadratic effects of temperature. Even when controlling for the temporal context, both land cover types were used more evenly than predicted from variation in availability (functional response in habitat selection). Use of two other land cover categories (pastures and moist areas) increased linearly with temperature and was proportional to their availability. The study shows that habitat selection by generalist foragers may be highly dependent on temporal variables such as weather, probably because such foragers switch between weather dependent feeding opportunities offered by different land cover types. An opportunistic foraging strategy in a landscape with erratically appearing feeding opportunities in different land cover types, may possibly also explain decreasing selection of the two most frequently used land cover types with increasing availability.

Seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios from hunter-based surveys

AbstractDemographic monitoring is vital for tracking and modelling the population dynamics of highly mobile bird populations. However, different types of monitoring can sometimes lead to different outcomes, and understanding the causes of equivocal results is an important step to advance future monitoring schemes. This study found consistent seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios among Danish hunter-based wing surveys, and describes how accounting for this variation might explain reported discrepancies between this and other monitoring methods. Early season flocks were dominated by adult males, and juvenile proportions were highest in November and significantly lower before and after this peak. Nationwide field assessments undertaken in January 2012 showed no significant differences from sex and age ratios in the wing survey data from that particular hunting season (2011/2012), indicating that this survey is a good predictor of Wigeon demography. These results highlight the need to account for consistent temporal variation in such demographic time series when using the results to model population parameters.ZusammenfassungJahreszeitliche Schwankungen in Geschlechterverhältnis und Altersstruktur bei der Eurasischen Pfeifente (Anas penelope) anhand von Erhebungen durch Jäger Für die Nachverfolgung und Modellierung populationsdynamischer Prozesse ist bei hochmobilen Vogelpopulationen ein demographisches Monitoring von entscheidender Bedeutung. Unterschiedliche Arten des Monitorings können jedoch gelegentlich zu unterschiedlichen Resultaten führen, und das Verständnis der Ursachen von mehrdeutigen Ergebnissen ist ein wichtiger Schritt in der Entwicklung zukünftiger Monitoring-Systeme. In den Erhebungen dänischer Jäger fanden sich durchgängig jahreszeitliche Schwankungen im Geschlechterverhältnis und in der Altersstruktur der Eurasischen Pfeifente (Anas penelope); diese Studie beschreibt, wie die Berücksichtigung solcher Unterschiede eventuell die Diskrepanzen zwischen den Ergebnissen aus unterschiedlichen Monitoring-Methoden erklären könnte. Schwärme zu Beginn der Saison wurden von adulten Männchen dominiert, während der Anteil junger Vögel im November am höchsten und vor und nach diesem Spitzenwert signifikant niedriger war. Im Januar 2012 landesweit durchgeführte Freiland-Bewertungen zeigten keine signifikanten Unterschiede im Geschlechterund Altersverhältnis zu den Erhebungen dieser speziellen Jagdsaison (2011/2012), was nahelegt, dass eine solche Erhebung ein guter Prädiktor für demographische Aussagen bei Pfeifenten ist. Diese Ergebnisse unterstreichen die Notwendigkeit, konsistente zeitliche Schwankungen in derartigen demographischen Zeitreihen zu berücksichtigen, wenn die Ergebnisse dazu benutzt werden, Populationsmerkmale zu modellieren.

Variation in Working Effort in Danish Little Owls Athene noctua

Locomotion is costly and should therefore serve a purpose according to the principle of optimal behaviour. In this light, we studied variation in nocturnal activity of radio-tagged Little Owls Athene noctua in Denmark where, after a decline of at least 30 years, the species is threatened with extinction. The study is based on 143 one-hour surveys of breeding and 274 surveys of non-breeding Little Owls (27 territorial individuals on 14 territories). Working effort is calculated as the total linear distance between all observed consecutive telemetry fixes during one-hour surveys (Minimum Flight Distance, MFD). The effort peaked during the post-hatching dependency period with males flying longer distances and having fewer inactivity periods than females. This might suggest that also after hatching, males provide more food to the nest than females. Non-breeding owls were completely inactive in 13% of all surveys. Probability of inactivity increased with heavy rain and was highest in the middle of the night. During the non-breeding season, MFD of active owls varied with a peak in March and a low in December, possibly reflecting seasonal variation in metabolic needs and social activity. During the non-breeding season, MFD was slightly higher for males than for females, possibly reflecting lower energetic flight costs due to lower weight, and were highest at the beginning and end of nights.

Functional Responses of Human Hunters to Their Prey — Why Harvest Statistics may not Always Reflect Changes in Prey Population Abundance

Harvest records are often assumed to offer an indirect measure of population abundance in huntable species. However, this requires population density changes are reflected in comparable linear changes in harvest rates. We tested this assumption for common snipe Gallinago gallinago, common wood pigeon Columba palumbus, coot Fulica atra, grey partridge Perdix perdix, roe deer Capreolus capreolus and brown hare Lepus europaeus in Denmark. If we consider hunting a form of predator—prey interaction, the annual kill can be viewed as a predator functional response to prey population size. Convergence of the annual kill to a type I functional response with similar auto-correlative structures in the harvest and count data would support the hypothesis that fluctuations in harvest and population abundance occurred with similar periodicity. The annual kill of common snipe showed the best fit to a type I functional response to the point count indices, with similar auto-correlative structures in the two variables. Other species showed different functional responses, the result of hunter behaviour, such as voluntary hunting restraint on species of concern and saturation effects from rapidly expanding abundant species. Relationships between the annual kill and population abundance were complex and incorporation of hunting legislation changes improved optimal model fits between harvest statistics and count data. Consideration of the validity of the underlying assumptions is necessary before harvest records are used as an index for population size. It is essential that detectability/accessibility of a species does not change systematically over time. Such bias may derive from habitat shifts, difference in timing of counts and hunting harvest, changes in migration patterns and annual reproduction and mortality. We recommend the continued collation of hunting harvest statistics, supported by sociological studies, to provide insight into the mechanisms that affect the hunting effort, to understand relationships between harvest statistics and population abundance.