Search

A subset of the bottlenose dolphin Tursiops truncatus gephyreus population in Laguna, southern Brazil, specialize in foraging cooperatively with fishermen. In this study, we describe reproductive parameters for these dolphins and investigate whether this specialized tactic generates reproductive advantages for females that frequently engage in this unusual behavior. We analyzed photo-identification data collected during 233 boat-based surveys during 2007–2009 and 2013–2017. From 27,808 high-quality photographs, we identified and tracked the fate of 24 reproductive females and 45 of their calves. Calving was found to be seasonal, with most births occurring in late spring/summer. The average crude birth rate was 0.09, and estimated fecundity was 0.17. The mean inter-birth interval was 2.09 (for all calves) or 2.43 years (for surviving calves only). Survival to 1 and 2 years estimated by the Kaplan–Meier method was 0.78 (95% CI 0.65–0.92) and 0.65 (95% CI 0.51–0.83), respectively—which represents a survival rate in the second year of 0.83. We investigated the potential influence of birth timing, resource availability, and maternal foraging tactic, home range size and frequency of interaction with fishermen on calf survival. Timing of birth was a significant predictor of calf survival. Giving birth close to the local mullet season would provide lactating females with increased seasonal prey resources, leading to increased calf survival. Due to our sample size (n = 9 cooperative and 15 non-cooperative females), we could not conclude whether or not the cooperative foraging tactic influences calf survival and female reproductive success. We emphasize the importance of long-term monitoring of populations to understand regional life history characteristics and provide accurate information for viability analyses. [ABSTRACT FROM AUTHOR]

Recent years have seen an increasing interest in individual behavioral variation. However, the implications of such variation for population dynamics are often unknown. We studied the dynamics of a bottlenose dolphin (Tursiops truncatus gephyreus) population from southern Brazil, where some individuals forage cooperatively with artisanal fishermen. We fitted mark‐recapture models to 10 yr of photo‐identification data to investigate the influence of this foraging specialization on dolphins' population parameters, controlling for sex and ranging behavior. We estimated adult survival to be high (0.949 ± 0.015 SE), weakly influenced by home range size, sex or the frequency of interaction with fishermen. The slightly higher survival probability for individuals with smaller home ranges could stem from the benefits of reduced spatial requirements implied by the specialized foraging. Foraging also influenced the probability of resighting individuals, and there was no temporary or permanent emigration. Abundance fluctuated slightly over the years from 54 (95% CI = 49–59) to 60 (95% CI = 52–69) individuals, with no evident population trend. Despite such apparent population stability, we confirm this population remains small and geographically isolated which may threaten its viability and the viability of its unusual, localized foraging specialization. Our study also illustrates how accounting for individual variation can portray animal population dynamics more realistically. [ABSTRACT FROM AUTHOR]

Ship strikes are one of the major threats to large whales worldwide. The potential impact from increasing vessel traffic therefore is a concern for the future of the Brazilian humpback whale ( Megaptera novaeangliae) population., In order to evaluate the risk of collision between large vessels and humpback whales along coastal shipping routes in the region of the Abrolhos Bank - the most important breeding ground for the species in the south-western Atlantic Ocean - commercial vessels were used as platforms of opportunity to monitor the coastal shipping routes., Humpback whale density along coastal routes was estimated through multiple covariate line-transect 'distance sampling'. The number of potential collisions per year was estimated using a model based on vessel size and speed, track lengths, population density and the surfacing behaviour of whales., During the peak of the 2011 breeding season, whale density on the coastal route between Belmonte and Caravelas was estimated to be 0.085 whales km-2 and between Caravelas and Barra do Riacho, 0.023 whales km-2., The three commercial vessels operating in coastal waters between Belmonte and Barra do Riacho had the potential to collide with 25 humpback whales in total, and kill 17 of these, during the 2011 breeding season., As vessel traffic increases in the Abrolhos Bank region and humpback whale population grows, the likelihood of a vessel collision will increase., A simple and effective framework to study how changes in whale density will affect their vulnerability to ship strikes, and ensure the suitability of alternative shipping routes is presented, while evaluating whether additional mitigation measures are necessary, such as speed limits in areas or periods with higher densities of whales., Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]