Herzing, Denise L.

This study examined the coefficients of association (COAs) of Atlantic spotted
dolphins, Stenellafrontalis, in the Bahamas that have been part of a long-term
underwater observational study since 1985. First, three social units were designated based
on analysis of association indices. The units appeared to coincide with clusters of
individuals with similar ranges; however, there were insufficient ranging data to
determine whether the social units were separate geographical units. The associations
within and between these social units were analyzed to determine whether the units
comprised separate communities. Results indicated that separate communities did not
exist. Analysis of association indices of the 26 individuals with known relatives
demonstrated that there is preferential association among kin. Also, effects of social
segregation based on sex and age class, which are evident in the population as a whole,
are absent in kin dyads.

Two sympatric species of dolphins (Atlantic spotted dolphins, Stenella frontalis
and Atlantic bottlenose dolphins, Tursiops truncatus) have been long-term residents to
Little Bahama Bank. This study assessed whether there was a change in residence
patterns or diurnal foraging depths of bottlenose dolphins following a large emigration
event in the resident spotted dolphin community on this sandbank. Photo-identification
was used to identify individual bottlenose dolphins and compare pooled years before
(2010-2012) and after (2013-2015) the spotted dolphin emigration. The identified
community size and overall residency of the bottlenose dolphins remained similar,
although two bottlenose dolphins emigrated over deep water to the site spotted dolphins
emigrated. Bottlenose dolphins diurnally fed in shallower water but remained in the same
geographic foraging locations. Reasons remain unknown for this depth change, but
potential changes in the productivity of primary bottlenose dolphin foraging habitats or
reduction of spotted dolphins from shallower depths remain possibilities.

Between August 2005 and December 2006, 139 boat surveys were conducted in
Sepetiba Bay, Brazil to sample behavioral patterns and environmental parameters during
the occurrence of marine tucuxi groups and aggregations. Aggregations were defined as
several groups gathered in an area totaling more than 100 animals, usually engaged in a
specific behavior. A total of 65 aggregations (x=177) and 192 groups (x=18) were
recorded. Marine tucuxi groups and aggregations differed regarding behavioral activity,
geographical location and age composition. Aggregations were temporal associations of
several marine tucuxi groups performing foraging/feeding activities probably in response
to prey species, abundance, and distribution. Aggregations were primarily located at the
interior of the Bay where local topography may aid dolphins in pursuing and herding
schools of prey. Presence of neonates and calves was highly correlated with aggregations,
reflecting the potential importance aggregations have in the protection, developmental
and learning processes of younger animals.

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.

Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops
truncatus) are two sympatric species resident to the Bahamas. The visibility of the
Bahamian water provided a unique opportunity to study spotted dolphin communication
during aggression. This study’s main focus was to decipher any similarities or differences
in the behaviors used by spotted dolphins during interspecific and intraspecific
aggression. Both similarities and differences were discovered. Biting, following, and
chasing behavioral events were used more during interspecific aggression, while the
display behavioral class was used more than the contact behavioral class during intrabut
not interspecific aggression. This study showed that spotted dolphins use more energy
intensive and risky behaviors when fighting interspecifically. This could result from
having to fight and defend females from a larger species, trying to avoid sexual
harassment from bottlenose males, or needing to use behaviors that are more overt and easily understood during interspecies communication.

Synchrony between Atlantic spotted dolphins (Stenella frontalis) is crucial for successfully
fending off bottlenose dolphins (Tursiops truncatus) during interspecies aggression. The present study
examined synchrony in adult Atlantic spotted dolphins during aggressive encounters with bottlenose
dolphins. Across group size, aggressive behavioral events increased preceding synchrony, peaked during
synchrony, and decreased dramatically after synchrony. Although smaller groups (< 10 dolphins) became
synchronous more frequently than larger groups (> 10 dolphins), larger groups remained synchronous
longer; however, smaller groups exhibited more frequent aggressive behavioral events during synchrony,
suggesting that additional aggressive behaviors may be necessary to compensate for the small group size, whereas larger groups may be able to rely on synchrony alone. Disorganized squawk bouts synchronized as physical synchrony began, but only if coupled with escalating aggressive behaviors. The synchrony during aggressive episodes observed in adult Atlantic spotted dolphins can be used as a baseline to determine the process of the development of this critical skill in juveniles.

The signature whistles of related Atlantic spotted dolphins ( Stenella frontalis) in the Bahamas were evaluated for similarity. Judges compared the contour patterns of signature whistles pair-wise between 19 dolphins. Whistle parameters between the signature whistles of individuals were statistically compared. There were no significant differences between the signature whistles of male and female calves when the similarity of their whistles was compared to their mothers. However, there was a tendency with female calves more likely to produce signature whistles similar to their mothers' whistles. Three out of five female calves produced signature whistles that were "very similar" or "similar" to the signature whistles of their mothers. Two out of four male calves produced signature whistles that were "similar" to the signature whistles of their mothers. The signature whistles of mother and calf pairs were more likely to be "similar" to each other than the signature whistles of sibling pairs.

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 investigation is the first to focus on the underwater behaviors and development of free-ranging Atlantic spotted dolphin (Stenella frontalis) mothers and calves. Underwater video recordings of 30 mother/calf pairs, during the calves' first three years of life, and 10 additional videos of four-year-old calves, were analyzed. Behavioral event frequencies were compared to the calf's age bracket (i.e. year-one, two, three and four). Results demonstrate an increase in calf independence in year-four shown by a significant reduction in Nursing Act behaviors, significantly more Feeding/Foraging behaviors, and increased behaviors performed in the proximity of individuals other than the mother or alone. No strong evidence was found for increased maternal rejection behaviors near the end of the estimated weaning period. Additionally, results indicate that, for select behaviors, synchronicity may be increasingly expressed over time. Few differences in behavioral frequency and type were observed between calf genders and between mothers of each gender.