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In this pilot study, we estimate roe deer Capreolus capreolus density in a fragmented landscape, using radio-tracking and direct observation in a Petersen-Lincoln framework with the joint hypergeometric maximum likelihood estimator. We used radio-tracking to obtain a direct count of the number of marked animals potentially observable in a given sample area, thus avoiding edge effects. We then carried out a coordinated observation survey, including drive beating, to ascertain the proportion of marked roe deer in the population sampled and thus generate a population estimate. Surveys were repeated three times in four sample blocks within the fragmented landscape, and estimates were compared to a sample block of a central forest in the same area. In general, roe deer are difficult to observe and census, but our experimental set-up in the fragmented landscape enabled us to observe on average 75% of marked animals present in a given survey (compared to 21.5% in the central forest). The variability in capture probability between individuals was low as three quarters of all marked individuals were observed in all, or all but one, of the surveys. Density estimates were largely similar across the sample blocks of the fragmented landscape (4.0-7.9 deer/100 ha), but lower than in the central forest (34.3 deer/100 ha). The variability of daily population estimates was quite low and similar in the fragmented landscape (CV of 25.9%) and the central forest (CV of 25.3%). Taking availability of woodland into account, the density in the fragmented landscape was as high, or higher, than in the central forest, reaching an exceptional 145.3 deer/100 ha of woodland in one survey area.

Abstract Studies on wild Eurasian lynx (Lynx lynx) have revealed variation in reproduction between areas, years and individuals. In order to explore potential causes for this variation other than food supply, we analysed data from captive lynx, which provide conditions with minimal environmental variation as all were fed ad libitum. Data from 37 individual female lynx were available from 20 zoos in Norway, Sweden, Finland, Switzerland and the Czech Republic. Data on 177 reproductive events (where a male was available to the female at mating time) are presented. Of these events, 85% resulted in litters being born. Average litter size was 1.95, with a variation from 1 to 4. The mean birth date was 26th May, and sex ratio was not significantly different from parity. The probability of reproduction was related to age, with fewer litters produced by the very young (2–3-year old), and no sign of a senescence effect. However, a clear effect of senescence on litter size was evident. The captive lynx did not have higher reproductive rates than wild lynx, indicating that either factors other than food supply are driving the variation in wild lynx reproduction, or that a factor such as stress may be causing additional variation in the captive population.

Births are highly synchronized among females in many mammal populations in temperate areas. Although laying date for a given female is also repeatable within populations of birds, limited evidence suggests low repeatability of parturition date for individual females in mammals, and between-population variability in repeatability has never, to our knowledge, been assessed. We quantified the repeatability of parturition date for individual females in five populations of roe deer, which we found to vary between 0.54 and 0.93. Each year, some females gave birth consistently earlier in the year, whereas others gave birth consistently later. In addition, all females followed the same lifetime trajectory for parturition date, giving birth progressively earlier as they aged. Giving birth early should allow mothers to increase offspring survival, although few females managed to do so. The marked repeatability of parturition date in roe deer females is the highest ever reported for a mammal, suggesting low phenotypic plasticity in this trait.

We investigated age-specific variation in male yearly breeding success (YBS) using genetic estimates obtained from 2 populations of a territorial ungulate, the European roe deer (Capreolus capreolus). YBS in both populations was markedly age-structured, with 3 distinct stages, supporting the dome-shaped pattern of variation commonly reported for age-dependent variation in life-history traits of ungulates. YBS was low at 2 years of age, peaked at 3–8 years of age, and tended to decline afterwards (senescence). Most males successfully reproduced for the 1st time at 3 years of age, which is well after their physiological maturity. The few successful young males (i.e., 2 year olds) were likely fast-growing individuals that could successfully hold a territory. The high variance in YBS and antler size for old males at Bogesund, Sweden, suggests that only some males of this age Class are able to maintain large antlers and, hence, retain their territories.