Management systems allowing free nest access are widely used in commercial rabbit breeding, but these produce a potential conflict with the doe's behavioural goal of a closed nest entrance. Furthermore, the restricted space in commercial breeding units prevents the doe from achieving a sufficient distance between her and the nest, another highly adaptive behavioural goal. This can lead to behavioural problems and pup mortality higher than 20%, attributable to hypothermia, injuries, weakness caused by the scattering and crushing of pups, or even cannibalism. In this study we tested a type of nest entrance (a metal cat-flap) that visually closed the nest box while still allowing the doe free access during the first 15 days after parturition. The effects of a cat-flap access (group CF) and of a permanently open nest box (group O) on nest-related behaviour, general activity, and plasma corticosterone concentration of the does, and on the mortality and weight of the pups, were compared using 15 ZIKA does in each group. Over 24 h, there was no difference between the groups in the frequency of ‘nest controls’ (approaches or entries to the nest without nursing of pups). However, outside nursing hours, does in group O showed more ‘head contacts’ with the nest, whereas does in group CF performed more nose contacts and nesting activities outside the nest. Does in group O performed twice as many potentially disturbing nest contacts in this time than does in group CF and had a higher increase of corticosterone after the administration of exogenous adrenocorticotrophic hormone. Pup mortality from days 16 to 35 was significantly higher in group O, and pups born to does in group O left the nest earlier. There was no significant difference in the weaning weights of pups between the two groups. As does with a cat-flap at the nest entrance still showed repeated nest approaches, the cat-flap possibly did not block all nest stimuli from the does. Alternatively, it is possible that the repeated approaches to the next box result from its being one of very few attractive or interesting features in an otherwise barren environment. Removal of the nest box from the cage is an effective method to eliminate nest stimuli, but this increases work for the staff without improving the barren environment for the rabbits. A better way of increasing the distance between the doe and the nest, as well as presenting a number of other attractive features, is group-housing of does.

Pup mortality and the timing of birth of South American sea lions Otaria flavescens were investigated to determine the possible relationship between fluctuations in prey availability in the Peruvian upwelling ecosystem and current and future reproductive success of sea lions during six consecutive breeding seasons. Our study from 1997 to 2002 encompassed the strongest El Niño on record and one La Niña event. Pup mortality ranged from 13% before El Niño to 100% during El Niño, and was negatively correlated with prey availability. Abortions were also more frequent when prey availability was low. However, pup mortality remained high following El Niño due to the punctuated short-term effects it had on population dynamics and subsequent maternal behaviour. Births occurred later in the season after years of low food availability and earlier following years of high food availability. The peak of pupping occurred around the peak of mortality in all years, and may have been the product of intensive competition between bulls at the peak of the breeding season. The stronger and more frequent El Niños that appear to be occurring along the Peruvian coast may produce significant stochastic changes in future births and pup mortality, which may place the vulnerable South American sea lion population in Peru at greater risk.

Pre-weaning pup mortality of grey seals Halichoerus grypus in a breeding colony (North Rona, Scotland, U.K.) was examined in relation to the density of local adult females over two breeding seasons. Accurate, fine-scale maps of daily seal locations within a GIS database permitted the extraction of measures of female density determined at a range of spatial scales from 5 to 50 m around each pup on the date of death. Adult densities around live pups provided the null distribution of adult densities, which were tested against the distribution of densities where deaths occurred. Pre-weaning pup mortality at this colony was not related to any of our density measures. The proportion of pups dying each day showed no seasonal trends. Analysis of topographic features from a sub-meter digital terrain model for locations where deaths occurred suggested that there were fewer mortalities in prime pupping habitats. This could have been a direct effect of habitat or the relative quality of mothers in these habitats. The distance separating mothers and pups tended to be greater on the periphery of the colony compared to more central areas. Pups in the peripheral areas may be more exposed to predation by gulls.