Critical factors for the recovery of marine mammals

{en} Over the past decades, much research has focused on understanding the critical factors for marine extinctions with the aim of preventing further species losses in the oceans. Although conservation and management strategies are enabling several species and populations to recover, others remain at low abundance levels or continue to decline. To understand these discrepancies, we used a published database on abundance trends of 137 populations of marine mammals worldwide and compiled data on 28 potentially critical factors for recovery. We then applied random forests and additive mixed models to determine which intrinsic and extrinsic factors are critical for the recovery of marine mammals. A mix of life‐history characteristics, ecological traits, phylogenetic relatedness, population size, geographic range, human impacts, and management efforts explained why populations recovered or not. Consistently, species with lower age at maturity and intermediate habitat area were more likely to recover, which is consistent with life‐history and ecological theory. Body size, trophic level, social interactions, dominant habitat, ocean basin, and habitat disturbance also explained some differences in recovery patterns. Overall, a variety of intrinsic and extrinsic factors were important for species’ recovery, pointing to cumulative effects. Our results provide insight for improving conservation and management strategies to enhance recoveries in the future.     

Effects of incubation temperature on behavior of hatchling pine snakes: implications for reptilian distribution

Summary Incubation temperatures in vertebrates affect incubation periods, and in some reptiles incubation temperature determines sex ratios and some limited behavior. Here I present evidence that incubation temperature in pine snakes (Pituophis melanoleucus) affects not only incubation periods and posthatching behavior in the laboratory, but also the behavior of hatchlings required for successful emergence and survival. These behavioral differences have evolutionary implications for selection of hatchlings from particular temperature nests. With increasing temperature, incubation periods decreased in the laboratory. In addition, incubation temperature affected hatching and emergence times as well as movement speed and foraging ability. Hatchlings from medium temperature conditions emerged from nests in the field in less time than hatchlings incubated at high or low temperatures, and hatchlings from low temperatures moved slower and were less able to capture and eat mice in the laboratory than hatchlings incubated at medium or high temperatures. Taken together, these laboratory and field experiments suggest that hatchlings from low temperature nests, compared to those from higher temperature nests, would be less able to emerge, find food, and locate hibernation sites prior to the onset of cold temperatures in the New Jersey Pine Barrens. These results suggest that incubation temperature affects a whole range of behavior and that distributional ranges of reptiles and other poikilotherms could be affected by summer temperatures (via incubation period and subsequent behavior) as well as ambient winter temperatures.     

Unequal sex ratios and their consequences in Herring Gulls (Larus argentatus)

Summary We observed the sex ratios and age composition of courting, nesting, and nonbreeding birds (in clubs) in four breeding colonies of Herring Gulls in Maine and New York. Breeding pairs, with eggs or chicks, often contained an immature male, but rarely contained an immature female. Similarly, courting pairs contained immature males, but rarely immature females. A higher proportion of courting pairs contained immatures compared with pairs with eggs or chicks. In all four colonies there was an excess of females in the clubs. A simulated colony which assumed unequal survival for males and females had an age ratio for unpaired birds that was similar to the observed values. We conclude that in Herring Gulls, mate competition exists and stems in part from an unequal tertiary sex ratio.     

Sexual selection and reproductive careers in mandrills (Mandrillus sphinx)

In sexually dimorphic, polygynous species, where males provide little parental care and competition between males for access to fertile females is high, sexual selection theory predicts sex differences in age-specific reproductive output and mortality profiles, and greater variance in lifetime reproductive success in males than in females. We examined age-specific reproductive output, mortality patterns and the extent and causes of variation in reproductive success for a semi-free-ranging colony of mandrills (Mandrillus sphinx, Cercopithecidae) in Franceville, Gabon, using long-term (20 year) demographic records and microsatellite parentage analysis. Although differences in the demography and feeding ecology of this closed, provisioned colony, in comparison with wild mandrills, limit interpretation of our results, sex differences in reproductive output and mortality showed the patterns predicted by sexual selection theory. Mortality was higher in males than in females after sexual maturity, and lifespan was significantly shorter in males (mean 14 year) than in females (>22 year). Age at first reproduction was significantly earlier in females (mean 4.2 year) than in males (11.6 year), and male reproductive output declined earlier. All females of breeding age produced offspring; while only 17 of 53 sexually mature males (32%) sired. Males sired a maximum of 41 offspring, versus 17 in females, and variance in male reproductive output was significantly greater than in females at all ages. The most important influence on variation in lifetime reproductive output in both sexes was joint variation between length of the breeding period and reproductive rate, due to lower reproductive rates in younger animals. Finally, social rank significantly influenced reproductive output in both sexes: high-ranking females began their reproductive careers earlier and had a higher subsequent reproductive rate than low-ranking females, while males that achieved top rank during their career sired far more offspring than males that did not.Electronic Supplementary Material Supplementary material is available for this article at     

The effects of male–male contests and female eavesdropping on female mate choice and male mating success in the jumping spider, <Emphasis Type="Italic">Thiania bhamoensis</Emphasis> (Araneae: Salticidae)

In experiments that comprised of three phases (fight, choice, and mating) under “seen” and “unseen” conditions, we examined the effects of the outcomes of male–male contests and female eavesdropping on female mate choice and male mating success in the fighting spider, Thiania bhamoensis (Salticidae). The results revealed female eavesdropping on agonistic interactions. Females that had watched an aggressive interaction showed no distinctive preference for the winner over the loser, but they preferred the loser when they had not observed a fight. Winners, however, achieved a greater mating success than did losers during the mating phase. Gaining access to females was based on the insistence of the winners in courtship in terms of the number of quivers, rather than on the fighting behavior of the males. Hence, the outcome of male–male contests may not be an important determinant of a male’s mating success in T. bhamoensis. Instead, courtship display plays an important role in determining the success of male mating in this species. This study also suggests that female mate preference may not be a good indicator of eventual female mate choice and male mating success. Thus, a causal relationship between female mate preference and male mating success cannot be inferred. Joanna P. Y. Chan, Pei Rong Lau, and Ai Jie Tham contributed equally.     

Meta‐Analysis of the Effects of Human Disturbance on Seed Dispersal by Animals

Animal‐mediated seed dispersal is important for sustaining biological diversity in forest ecosystems, particularly in the tropics. Forest fragmentation, hunting, and selective logging modify forests in myriad ways and their effects on animal‐mediated seed dispersal have been examined in many case studies. However, the overall effects of different types of human disturbance on animal‐mediated seed dispersal are still unknown. We identified 35 articles that provided 83 comparisons of animal‐mediated seed dispersal between disturbed and undisturbed forests; all comparisons except one were conducted in tropical or subtropical ecosystems. We assessed the effects of forest fragmentation, hunting, and selective logging on seed dispersal of fleshy‐fruited tree species. We carried out a meta‐analysis to test whether forest fragmentation, hunting, and selective logging affected 3 components of animal‐mediated seed dispersal: frugivore visitation rate, number of seeds removed, and distance of seed dispersal. Forest fragmentation, hunting, and selective logging did not affect visitation rate and were marginally associated with a reduction in seed‐dispersal distance. Hunting and selective logging, but not fragmentation, were associated with a large reduction in the number of seeds removed. Fewer seeds of large‐seeded than of small‐seeded tree species were removed in hunted or selectively logged forests. A plausible explanation for the consistently negative effects of hunting and selective logging on large‐seeded plant species is that large frugivores, as the predominant seed dispersers for large‐seeded plant species, are the first animals to be extirpated from hunted or logged forests. The reduction in forest area after fragmentation appeared to have weaker effects on frugivore communities and animal‐mediated seed dispersal than hunting and selective logging. The differential effects of hunting and selective logging on large‐ and small‐seeded tree species underpinned case studies that showed disrupted plant‐frugivore interactions could trigger a homogenization of seed traits in tree communities in hunted or logged tropical forests. Meta Análisis de los Efectos de la Perturbación Humana sobre la Dispersión de Semillas por Animales