Structure and growth of the baculum (os penis) in arctoid carnivores have been well described for many species. This study presents the first extensive analysis of bacular growth and variation for bears (Ursidae), based on 871 bacula of polar bears Ursus maritimus (858 of known age) that were shot in the Canadian Arctic from 1994 to 1997. Bacular length, maximal diameter and mass increased from 109 mm, 5.93 mm and 2.68 g respectively in 1-year-old bears (n = 34) to 190 (maximum 222) mm, 18.7 (24.4) mm, and 20.4 (31.9) g respectively in bears≥10 years of age (n>200). Bacular length is ∼8% of body length in adults. Bacula were moderately variable in size: coefficient of variation for length, diameter, and mass1/3 were 5.2, 10.0 and 5.4% respectively (16.3% for mass). No geographic variation in size was apparent. Bacula reached asymptotic size at 8–9 years of age. At physiological sexual maturity (∼6 years of age), bacula were at 89, 73 and 62% of asymptotic length, diameter and mass respectively (compared with body length at ∼95%). Interpretation of these findings must await behavioural and physiological information on courtship and copulation in the polar bear, and comparative data on other ursids.

Journal of Zoology Volume 260 Part 4, August 2003 (pages 391–403)

Linear enamel hypoplasia (LEH), a deficiency in enamel formation visible on mammal tooth crowns, can be used as a retrospective indicator of physiological stress and developmental health in humans and animals. In this first study, for north-western Europe, the condition has been recorded from prehistoric (mesolithic) and recent populations of wild boar, and from domestic pigs belonging to early farming (neolithic) communities. It was possible to show that LEH occurs in recent and ancient populations of wild boar from north-west Europe, and that the occurrence of the condition can be explained by the same events within the animal's life (birth, weaning, winter starvation) as has been previously suggested for archaeological domestic pig samples. The frequency of LEH is consistently low within all ancient and recent populations of wild boar studied, a remarkable observation given the pronounced differences in the living conditions of these two diachronically well-separated groups, mainly linked with the increasing human pressure on recent populations of wild animals. Early domestic samples generally show high LEH frequencies, although considerable variation exists between the samples. It is suggested that these high frequencies are, in general, the result of domestication, while the variation could be related to differences in early husbandry. The observation of LEH, therefore, provides a valuable tool for studying the history of animal domestication.

In ungulates, males and females have contrasting life histories, as usually only the females raise the young. How reproductive effort in males varies with individual level and population level characteristics has received little attention in the literature. Using published information on direct (weight loss during the rut) and indirect (rut-related changes in activity budgets, fighting frequency, etc.) measures of reproductive effort, we tested whether effort in males increased with (H1) increasing age, (H2) increasing body size, (H3) decreasing population density, (H4) increasingly female-biased sex ratio and with a younger male age structure. Consistent with H1, reproductive effort was consistently higher in prime-aged than in younger males in a large number of studies. Among younger males, sub-adult males had an equal or higher effort than yearling males. Prime-aged males had more typical rutting behaviour (e.g. roaring, tending, fighting and chasing frequencies) and they often lowered their intake of forage during the rut. However, reproductive effort usually declined for very old age classes. Reproductive effort increased with size (H2) also after accounting for age. Data on effort vs (H3) density and (H4) sex ratio/male age structure were inconclusive. Clearly, far more studies relating effort to population characteristics are needed before the rutting ecology of male ungulates can be understood.

Journal of Zoology Volume 263 Part 1, May 2004 (pages 31–39)