Social behavior in animals

Animals display a remarkable variety of social behaviors that are necessary for survival. Despite the importance of social behaviors, the neurobiological mechanisms underlying the evolution of such behaviors are largely unknown. The Mexican tetra, Astyanax mexicanus, is a powerful model for studying how behaviors evolve, including social behavior. A. mexicanus exists as a schooling surface form and a non-schooling cave form. Here we have utilized this model in order to investigate how differences in the behavior of individuals result in differences at the level of emergent group social behaviors. We begin by reviewing how fish have contributed to the study of social behavior in Chapter 1, then continue to dissect differences in the schooling and shoaling behavior of adult surface and cave fish in Chapter 2, and finally address ontogenic differences that result in these differences in Chapter 3. All-in-all this, work reveals how evolution may act on the behavior of individuals to produce differences in relevant group behaviors.

Personality is defined as inter-individual variation of behavioral traits while
maintaining intra-individual stability. The focus of this study was to observe distinct
personality trait categories, establish baseline personality trait phenotypes for the juvenile
population, and compare the personality phenotypes between different categories, such as
sex or generation. Three personality traits were studied—sociability, curiousity, and
boldness—based on the percentage of time individuals spent with conspecifics, human
researchers, and their mothers, respectively. The surveyed individuals significantly
varied positively and negatively from the means of each trait, and no significant
difference for any trait was found between males and females, or across time periods. A
moderately strong correlation was discovered between two personality traits, boldness
and curiousity, suggesting a personality syndrome. The second primary goal was to use
the aforementioned baseline to determine if personality traits can be used to predict neophilic behavior specific to human-dolphin communication research. Six of the study
subjects were more prone than their peers to engage with the two-way work, and these
individuals were more bold—spent less time with their mothers—than the other subjects.
This suggests that boldness has some predictive capabilities towards this type of
neophilia.

The present study examined the alteration of benthic foraging behavior by mother Atlantic spotted dolphins (Stenella frontalis) when foraging in the presence of their calves in comparison to the foraging behaviors of the mothers when the calves were not present. The mother dolphins chased prey significantly longer and made significantly more body-orienting movements during foraging in which calves were present. In 5 of the events where the calves were present the prey was not eaten by the mother, but instead the calves were allowed to pursue the prey and were confirmed to have eaten the prey in 3 of the foraging events, even though the calves were still nursing. Additionally, this altered foraging behavior only occurred in the presence of their naive calves. Therefore, the present study may be evidence of teaching as a potential social learning mechanism of foraging behavior by Atlantic spotted dolphins.

This study reports on a community of bottlenose dolphins found >27 km from Grand Bahama Island. Observations were conducted from May--September, 1993--2002. The half weight index determined coefficients of association (COA) between dolphins for each year and from pooled data over the 10-year period. Long-term site fidelity of up to 17 years occurred. Resident and non-resident dolphins occurred in the area. Some dolphins traveled 333 km between communities. Average group size was 3--5, and significantly larger with calves. Traveling groups were significantly smaller than feeding or socializing. Mother-calf associations were the strongest. Male-male COAs were low (x = .34), however, some individuals formed strong associations. Female-female COAs were low (x = .35), and affected by female reproductive status. Mixed-gender COAs were significantly lower (x = .31) than same sex associations. Pooled data revealed lower COA values, however, the same trends were evident. The long-term associations revealed from yearly COAs were not seen when data were pooled.

This study documented the behavioral development of Atlantic spotted dolphins (Stenella frontalis) in the Bahamas. 45 three-minute video-taped sequences of underwater social behavior (aggression, courtship, play), spanning from 1992 to 1996, were selected for ethological analysis and were broken down into 15 adult, 15 juvenile and 15 mixed age class sequences. Continuous focal sub-group sampling was conducted, and one-tailed Kruskal-Wallis ANOVAs were used to test for differences between the age groups in frequencies of occurrence of: (1) the 7 behavioral categories, and (2) the 8 most frequently performed behavioral events. Juveniles performed significantly more Other behaviors and Attention to Object events than adults, suggesting the importance of play within this social species. A Mann-Whitney U test revealed that within mixed age classes, behaviors were performed within combined-age-class groups more often than within single-age-class groups, suggesting a participatory mode of learning within juveniles.

This study investigated a resident community of Atlantic spotted dolphins (Stenella frontalis) on Little Bahama Bank (LBB) in the Bahamas utilizing a noninvasive molecular approach. Genetic template material was collected and extracted from fecal material of S. frontalis. Fine-scale population structure was found within LBB according to mitochondrial DNA (mtDNA) and microsatellites (Fst = 0.25317, P < 0.0001 and Fst = 0.04491, P < 0.0001, respectively). Three main social clusters (North, Central, South/Roam) exist on LBB and all clusters were found to be genetically distinct according to microsatellite analyses. Mitochondrial haplotypes revealed North and South/Roam were not differentiated, but Central was different from both. When separated by sex, males were less genetically structured than females. Males showed no evidence of structure according to Ost or Rst.

The Major Histocompatibility Complex (MHC) encodes proteins critical to the vertebrate immune response; therefore MHC diversity is an indicator of population health. I have (1) Isolated exon 2 of the class II gene DQA in Tursiops truncatus in the North Indian River Lagoon (IRL) (n=17), South IRL (n=29) and adjacent Atlantic waters (n=20), (2) assessed genetic variability between groups, (3) developed a method to genotype individuals, (4) typed 11 unique alleles in 66 individuals, (5) detected geographic patterns of diversity between estuarine and coastal individuals (FST=0.1255, p<0.05), (6) found evidence of positive selection centered in the binding pockets P1, P6 and P9 of the peptide binding region (w=2.08), (7) found that patterns of polymorphism did not closely match patterns of diversity in neutral markers, (8) performed a pilot study with Orcinus orca. The initial findings highlight the need for further comparative work and suggest that silent mutations are not neutral.

Discipline was implemented by mothers and alloparent spotted dolphins (Stenella frontalis) mothers and alloparents on Little Bahama Bank, Bahamas. Disciplinarians were significantly more likely to be adults than juveniles. Although most disciplinarians were female, males were also observed to perform discipline. The recipients of discipline were male and female, and significantly more likely to be calves than juveniles. Pursuit, contact, and display behaviors were used in discipline, however pursuit behaviors were most often observed. Variables such as age class, sex, and parity were not found to influence how discipline was implemented. The durations of all disciplinary pursuits were under thirty seconds, and successful pursuits had slightly shorter duration than unsuccessful pursuits. Disciplinarian success was not significantly influenced by age class, sex, parity, or behavior used.

The purposes of this dissertation were to identify complex social-cognitive behaviors in a population of wild Atlantic spotted dolphins (Stenella frontalis) using long-term video archives and identify developmental trends in those behaviors. Chapter One analyzed calf behavior during foraging events involving maternal teaching in order to identify mechanisms for sharing information between mother and calf... The calves' behavior was affected by the referencing cues, supporting the presence of joint attention and true teaching behavior....Chapter Two observed the altered benthic foraging behavior of juvenile play groups, in which juveniles took turns chasing the fish and using referencing gestures to reference the position of the fish to other individuals during the chase, despite the ability of these young, independent dolphins to catch fish much more quickly and efficiently alson... The third chapter analyzed social object play in which dolphins passed pieces of seaweed between individuals. The data clarified developmental trends in the play, and suggested social-cognitive abilities needed for participation.

Persistent, anthropogenic contaminants collectively known as endocrine-disrupting chemicals (EDCs), are considered to be potential threats to wildlife reproductive fitness (Wingfield, 2002). The modes by which EDCs act on the reproductive system, and establishment of steroid profiles in wildlife, are important areas of study. Two means of performing an endocrine snapshot profile from dolphin tissues (serum and urine) were tested on samples, comparing a novel high performance liquid chromatography method to newly-validated enzyme-linked immunoassays (ELISAs). Serum and urine samples were obtained from two marine parks, and from free-ranging dolphins in the Indian River Lagoon (IRL) and Charleston Harbor (CHS) systems. Relative binding affinities of steroids versus putative EDCs to steroid receptors were compared in dolphin reproductive tissues, obtained by the Georgia Aquarium's Dolphin Conservation Field Station (GADCFS) from strained bottlenose dolphins (four male, three female) during 2010 and 20ll.........I conclude that endocrine disruptors are tissue and receptor specific, and both legacy and emerging contaminants are of concern to dolphin stocks, particularly those facing other significant environmental stressors.