Patterns of Social Affiliation and Group Composition for Bottlenose Dolphins (Tursiops truncatus) in San Luis Pass, Texas

Group sizes, group composition, and association patterns of bottlenose dolphins (Tursiops truncatus) were investigated in the San Luis Pass area (Sep. 1995- Aug. 1996) of the Galveston Bay Estuary to examine differences in community structure of individuals inhabiting different portions of the estuary. Group sizes (n = 83) ranged from 1 to 29 (x̄ = 10.6) and were seasonally variable, with the largest groups occurring in spring (x̄ = 16.3) and the smallest groups during the fall (x̄ = 6.3). Seventy-one individuals were identified using photoidentification, and the sex of six dolphins (three males, three females) was determined. At least 31 (48.4%) groups were of mixed sex. Twenty-nine dolphins that were identified five or more times were used to calculate half-weight coefficients of association (COAs), which ranged from 0.00 to 0.83 (x̄ = 0.46). Coefficients of association for male pairs were higher than COAs for female and mixed-sex pairs. Permutation tests were performed to test for nonrandom associations and presence of preferred or avoided companions. The null hypothesis of random association was rejected, indicating that dolphins preferentially associated with some individuals and avoided others. In all replicates, three known-male pairs had significantly large COAs. These preliminary results suggested that, excluding mother-calf pairs that were not examined, male pairs formed the most stable social bonds

Why do dolphins form mixed-species associations in the Azores ?

Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed-species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed-species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed-species groups were compared with those of single-species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed-species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed-species groups depends on several environmental factors, and therefore may constitute an adaptive response

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Occurrence and distribution of cetaceans in Sao Tome and Principe tropical archipelago and their relation to environmental variables

UID/HIS/04666/2013preprintpublishe