High site fidelity,strong associations,and long‐term bonds: Short‐finned pilot whales off the island of Hawai‘i

Studies of short‐finned pilot whales suggest they travel in stable mixed‐sex groups composed of strongly associated individuals; however, temporal analyses of social structure are lacking. To examine site fidelity, association patterns, and temporal relationships, we analyzed data from 267 encounters of this species off the island of Hawai‘i from 2003 through 2007, identifying 448 distinctive individuals (68.1% seen more than once). About 72% of the whales were linked by association into a single social network, suggesting the possibility of multiple populations using the area. Sighting histories suggested that only some individuals exhibit high site fidelity. Individuals demonstrated preferential associations and community division was strongly supported by average‐linkage hierarchical cluster analysis of the association data. Nine longitudinally stable social units composed of key individuals and their constant companions were identified. Qualitative assignment of age and sex classes of unit members indicated that some segregation between adult males and female/calf pairs may occur. Temporal analyses of individuals encountered on the same day indicate stable long‐term associations. Differential patterns of residency and site fidelity were unexpected and may be indicative of multiple populations around the main Hawaiian Islands. The presence of a resident population demonstrating strong, long‐term site fidelity and associations off Hawai‘i Island may warrant special management considerations.     

Social structure of Atlantic spotted dolphins,Stenella frontalis,following environmental disturbance and demographic changes

Extreme environmental events and demographic changes can have variable effects on the social structure of animal populations. This study compared the social structure of a community of Atlantic spotted dolphins in the Bahamas before and after two hurricanes. Approximately 36% of the individuals were lost, with no subsequent increase in immigration. The majority of the social structure characteristics were consistent with results from a long‐term study covering the previous 12 yr, including community structure with definitive social clusters, sex preferences and overall association patterns. However some changes occurred, though still constrained within sex preferences. Posthurricane there was a decrease in social differentiation and increased cohesion within clusters and across age class. Males retained or made new first order alliances, however, only one second order alliance was evident, revealing a simplified alliance structure. Juvenile individuals made alliance level associations, unprecedented from long‐term analysis. Although other studies have shown stark restructuring, this study showed that less drastic changes within overall social structure stability can occur. Persistence and evolutionary changes in populations through environmental and/or demographic perturbations may depend on the social structure of a population or community. Understanding the processes involved in social development is paramount for conservation of diverse populations.     

Long‐term social structure of a resident community of Atlantic spotted dolphins,Stenella Frontalis,in the Bahamas 1991–2002

Long‐term social structure data on small delphinids is lacking for most species except the bottlenose dolphin. This study describes the long‐term social structure of one community of Atlantic spotted dolphins, Stenella frontalis, divided into three social clusters. Data from 12 yr were analyzed using SOCPROG 2.3. Coefficients of association (CoA) were calculated using the half‐weight index. The overall mean community CoA ranged from 0.09 to 0.12. Temporal analyses and mantel tests revealed significant differences between sex class associations due to high male‐male CoA (0.12–0.23) compared to female‐female and mixed sex CoA (0.08–0.10). Female associations were strongly influenced by reproductive status, calf care, and social familiarity, but not by age class. Male associations were strongly influenced by age, access to females, and alliance formation. Males showed two levels of alliance formation, long‐term first order pairs/trios (CoA 0.70–1.00) and shorter‐term second order alliances between two or more first order alliances (CoA 0.45–0.69), and a possible third level during interspecies interactions. Mating strategies, sex, and cluster formation shaped the social structure in this spotted dolphin community. Similar to many bottlenose dolphin studies, long‐term affiliations for spotted dolphins were correlated with age, sex, and reproductive status.     

Response of southern right whales to simulated swim‐with‐whale tourism at Península Valdés,Argentina

Guidelines for sustainable tourism involving swimming with large whales are not well‐developed compared to those focused on programs of swimming with delphinids. From September to November 2005 and August to September 2006, we collected behavioral and movement data for southern right whales (Eubalaena australis) exposed to interactions with boats and swimmers at Península Valdés, Argentina. Whales were tracked from shore using a theodolite before, during, and after a series of directed interactions with swimmers and a boat. Resting, socializing, and surface active behavior decreased, traveling increased, and whales swam faster and reoriented more often during interactions. Responses were variable by age/sex class, with mother/calf pairs showing strongest responses. Increased levels of tourism activity are a concern, as reduction in resting time and disruption of socialization among adults, juveniles, and mother/calf pairs have unknown long‐term consequences. Additional data should be collected for whale behavior in proposed tourism and nontourism areas to build a long‐term database which can be used to determine if reactions of whales change over time. Our data suggest that swimming with whales in Chubut Province should not be legalized until further investigations are completed, especially in light of the recent southern right whale die‐offs recorded in Península Valdés.     

How does social behavior differ among sperm whale clans?

When individuals primarily associate with and learn from those who behave similarly, society and culture become closely tied. Sperm whales (Physeter macrocephalus) exhibit multilevel social structure, the levels of which are differentiated in part by characteristic cultural behaviors. Sperm whales are organized into sympatric clans, with distinctive vocal repertoires that are socially learned. Other behaviors, such as movement patterns and foraging, also differ among clans. Here we ask whether the clan partition also includes divergences in social behavior. Off the Galápagos Islands, members of two clans differed consistently in diving synchrony, heterogeneity, and temporal stability of social relationships. While number of associates (indicated by social unit, group, and cluster sizes) were similar between clans, Regular clan members dived more synchronously and had more homogeneous relationships than the Plus‐One clan members. Plus‐One social units had generally longer associations than those of the Regular clan. Differences in surface‐time coordination and quality of social relationships are likely byproducts of the clan segregation, which could affect alloparental care giving, therefore scaling up to differential calf survival rates between clans. This new dimension of behavioral divergence between sperm whale clans indicates that sympatric, socio‐cultural entities of nonhumans can also display characteristic social behavior.     

Community structure and cluster definition of Atlantic spotted dolphins,Stenella frontalis,in the Bahamas

Fission‐fusion dynamics typical of many delphinid populations allow for a variety of social grouping patterns. Identifying these groupings is crucial before conducting a detailed social structure analysis. This study analyzed the structure of a population of Bahamian spotted dolphins, Stenella frontalis. Through long‐term observations and preliminary analysis, three clusters were defined: Northern, Central, and Southern. To quantitatively investigate these delineations, we conducted analysis on 12 yr of sighting data using SOCPROG 2.3. Coefficients of association (CoA) were calculated using the half‐weight index, with individuals sighted six or more times per pooled period (3 yr each). Nonmetric multidimensional scaling (MD), hierarchical agglomerative cluster analysis and Mantel tests were conducted to determine if any divisions were present. Mantel tests and MD plots analysis supported the delineations into the three clusters. Cluster analysis showed cluster groupings, but with less clear distinctions between the clusters. The amount and strength of associations were significantly higher within clusters than between clusters. Based on behavioral and geographic overlap, these clusters did not meet the definition of separate communities and thus were termed social clusters. These fine scale, within community divisions, are biologically and socially important aspects of their community and are crucial in understanding the dolphins’ social structure.     

Social structure of killer whales (Orcinus orca) in a variable low-latitude environment,the Galápagos Archipelago

Killer whales (Orcinus orca) have strong social matrilineal bonds and form groups and long-lasting associations, but little is known about their population or social structure in an equatorial setting such as the waters around the Galápagos Islands. Using 91 encounters and identification photographs from 1991 to 2017, we identified 64 killer whales of which 18 individuals were locals with high resighting rates. Group size was small, ranging from 1 to 15 animals, with 69% of the groups containing four or fewer animals. Using social network analysis (SOCPROG 2.7) whales grouped into three distinct units and one loose association with frequent exchange between different groups. One male–male unit showed a strong association (association strength = 0.55). Overall, associations lasted over at least 3 years. Our data give first evidence of a loose social organization of Galápagos killer whales, similar to fission-fusion societies.     

Social Affiliations within Sperm Whale (Physeter macrocephalus) Groups

We examined patterns of affiliation within groups of sperm whales ( Physeter macrocephalus ), particularly concentrating on how short-term spatio–temporal associations reflect long-term relationships. Female and immature sperm whales live in stable, and partially matrilineal, social units. Two or more social units may move together for periods of several days, forming a cohesive group of about 20 animals. We observed that sperm whales in the eastern tropical Pacific quite consistently associated with members of their own social unit more than they did with other animals in their group with whom they did not share a long-term relationship. There was little evidence for preferred, or avoided, affiliations within social units, except in two large and relatively unstable units. In two well-studied groups, individuals did not show consistently favoured positions in the foraging rank relative to other members of their social unit. These results indicate the importance of long-term relationships to female and immature sperm whales, but suggest that relationships are quite homogeneous within social units.     

The social organization of resident-type killer whales (Orcinus orca) in Avacha Gulf,Northwest Pacific,as revealed through association patterns and acoustic similarity

Northeast Pacific resident-type killer whales (Orcinus orca) are known to form stable associations based on kinship between maternal relatives (matrilines) with a system of vocal dialects thought to reflect kinship relationships. We analyzed association patterns and acoustic similarity to study the social organization of killer whales in Avacha Gulf (Kamchatka, Russia), in the Northwest Pacific. The resident-type killer whales of Avacha Gulf formed temporally stable units that included maternal relatives with no dispersal observed. Acoustically, the killer whale community of Avacha Gulf was characterized by a system of dialects comparable to the communities of Northeast Pacific resident-type killer whales. Different units rarely associated with each other and these associations were nonrandom. Associations at different spatial levels did not always coincide with each other and with the patterns of acoustic similarity. Associations between units could change quickly irrespective of kinship relationships. The vocal dialect of a unit, which is more stable than the association patterns between units, might better reflect the overall kinship relationships. The stability and frequency of associations between units depended on the number of mature males in a unit, which could contribute to differences in the speed of change in vocal dialects and association patterns.     

Social communities and spatiotemporal dynamics of association patterns in estuarine bottlenose dolphins

Network analysis has recently been used to delve into the dynamics of cetacean sociality. Few studies, however, have addressed how habitat shape influences sociality, specifically how linear water bodies constrain the space where individuals might interact. We utilized network and spatiotemporal analyses to investigate association patterns and community structure in a bottlenose dolphin population in a linear estuarine system, the Indian River Lagoon (IRL), Florida. Using sighting histories from a multiyear photo‐identification study we examined association patterns for 185 individuals collected over a 6.5 yr period (2002–2008). The population was highly differentiated (S = 0.723) and organized into six distinct social communities (Q = 0.544), spread in an overlapping pattern along the linear system. Social organization differed between communities, with some displaying highly interconnected networks and others comprising loosely affiliated individuals with more ephemeral associations. Temporal patterns indicated short‐term associations were a significant feature of the fission‐fusion dynamics of this population. Spatial analyses revealed that social structure was shaped by an individual's ranging patterns and by social processes including preference and avoidance behavior. Finally, we found that habitat “narrowness” may be a major driving force behind the sociality observed.     

Occurrence of false killer whales (Pseudorca crassidens) and their association with common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand

On a global scale, false killer whales (Pseudorca crassidens) remain one of the lesser‐known delphinids. The occurrence, site fidelity, association patterns, and presence/absence of foraging in waters off northeastern New Zealand are examined from records collected between 1995 and 2012. The species was rarely encountered; however, of the 61 distinctive, photo‐identified individuals, 88.5% were resighted, with resightings up to 7 yr after initial identification, and movements as far as 650 km documented. Group sizes ranged from 20 to ca. 150. Results indicate that all individuals are linked in a single social network. Most observations were recorded in shallow (<100 m) nearshore waters. Occurrence in these continental shelf waters is likely seasonal, coinciding with the shoreward flooding of a warm current. During 91.5% of encounters, close interspecific associations with common bottlenose dolphins (Tursiops truncatus) were observed. Photo‐identification reveals repeat inter‐ and intraspecific associations among individuals with 34.2% of common bottlenose dolphins resighted together with false killer whales over 1,832 d. While foraging was observed during 39.5% of mixed‐species encounters, results suggest that social and antipredatory factors may also play a role in the formation of these mixed‐species groups.     

Long-term social structure of long-finned pilot whales (<Emphasis Type="Italic">Globicephala melas</Emphasis>) in the Strait of Gibraltar

The Strait of Gibraltar is inhabited by around 216 pilot whales, which are present all year round, and nothing is known about their social structure. The aim of this study is to analyse the inter-individual association patterns within this pilot whales community to (1) provide an insight on their long-term social system and (2) to assess the relationship between sexes within this social system. Between 1999 and 2006, 23,004 km was sampled in the Strait of Gibraltar, and 4,887 images of dorsal fins of pilot whales were taken from 226 groups. The sex of 56 of the individuals could be determined genetically. The strength of the behavioural relationships between dyads of individuals was calculated, and the temporal aspects of the social structure were evaluated, showing in a non-random social structure made by constant companions. The preferred associations between individuals consisted in associations of males–females. Eight long-term units could be found with different degrees of association rates. Consequently, we propose that, in the Strait, the pilot whales exhibit a hierarchical social system composed of a population encompassing several clans of pilot whales each containing several pods. Pods will then be formed by several line units, similar to killer whale matrilineal units.     

Dusky dolphin (Lagenorhynchus obscurus) social structure characterized by social fluidity and preferred companions

Many coastal delphinids exhibit social structures with a high degree of fission‐fusion dynamics. However, little is known about fission‐fusion dynamics in semipelagic delphinids such as dusky dolphins (Lagenorhynchus obscurus). We analyzed dusky dolphin social structure in a winter foraging habitat in New Zealand. We examined the population‐level societal attributes of preferred/avoided companions, behaviorally specific preferred/avoided companions, and simple ratio (SR) association index strength and distribution and the dyad‐level societal attribute of temporal patterning of associations. We identified 741 individuals; 99 met inclusion criteria for analysis. Long‐term and short‐term preferred/avoided companions were present in the pooled (6 yr) and annual samples. Individuals were observed to form long‐term but not short‐term preferred/avoided companions during all behavioral states. Mean and maximum SRs were 0.03 ± 0.01 SD and 0.40 ± 0.20 SD, respectively. Temporal analysis indicated that individuals associated preferentially throughout the study period. Dusky dolphins exhibited high social fluidity, as indicated by many weak and few strong associations. However, there was stability as individuals were observed to form behaviorally specific preferred/avoided companions and associate preferentially throughout the 6 yr period. Dusky dolphins thus display a dynamic social structure where overall low levels of bonding are juxtaposed against a subset of the population that forms strong bonds.     

Herd composition,kinship and fission–fusion social dynamics among wild giraffe

A variety of social systems have evolved as a consequence of competition and cooperation among individuals. Giraffe (Giraffa camelopardalis sp.) societies are an anomaly because the dearth of long‐term data has produced two polar perspectives: a loose amalgamation of non‐bonded individuals that sometimes coalesce into a herd and a structured social system with a fission–fusion process modifying herd composition within a community. We analysed 34 years of data collected from a population of Thornicroft's giraffe (G. c. thornicrofti, Lydekker 1911) residing in South Luangwa, Zambia, to establish the nature of giraffe society. Our sample consisted of 52 individually recognized animals. We found that giraffe herd composition is based upon long‐term social associations that often reflect kinship, with close relatives significantly more likely than non‐relatives to establish herds. Mother/offspring dyads had the strongest associations, which persisted for years. Giraffe live in a complex society characterized by marked flexibility in herd size, with about 25% of the variance in herd composition owing to kinship and sex. We suggest that giraffe herds share many characteristics of fission–fusion social systems and propose that sophisticated communication systems are a crucial component regulating subgroup dynamics.     

Assessment of wound healing of tagged gray (Eschrichtius robustus) and blue (Balaenoptera musculus) whales in the eastern North Pacific using long‐term series of photographs

Tags have been used to examine migration routes and habitat use of large whales for >40 yr, however, evaluation of tag wound healing has largely been short‐term, anecdotal or generalized. This study developed methods for systematic photographic assessment of long‐term external consequences of tag placement, to determine potential differences in wound healing between species and tag types and thus advise future tagging efforts to possibly minimize undesirable side effects. Tag site appearance and healing characteristics were evaluated by two reviewers and a time series evaluated by five veterinarians from photographs during 995 postdeployment encounters with 34 gray and 63 blue whales tagged in the North Pacific. Blue whale resightings were less frequent, but spanned a longer time period due to earlier tag deployments than the more frequent gray whale follow‐up observations. Swelling occurred in 74% of reencountered gray whales, with the highest frequency 6 mo postdeployment. Swellings were common in blue whales with early tag designs but rare with current models. Depressions occurred in 82% of gray and 71% of blue whales. This study demonstrates the value of follow‐up studies of tagged animals and systematic scoring of photographs to quantitatively compare tag response.     

Temporal patterns in the social network of core units in Rwenzori Angolan colobus monkeys: Effects of food availability and interunit dispersal

1. Multi‐level societies are complex, nested social systems where basic social groups (i.e., core units) associate in a hierarchical manner, allowing animals to adjust their group sizes in response to variables such as food availability, predation, or conspecific threat. These pressures fluctuate over time and examining the extent to which this variation affects the clustering of core units into different tiers may be instrumental in understanding the evolution of multi‐level societies.
2. The goal of our study was to determine the degree of temporal variability in interunit associations in a multi‐level society of Rwenzori Angolan colobus monkey (Colobus angolensis ruwenzorii), and to determine the social and ecological factors that underlie association patterns. The C. a. ruwenzorii multi‐level society consists of at least three tiers, with core units clustering into clans that share a home range in a band tier.
3. We performed social network analyses on 21 months of association data from 13 core units (totaling 139 identifiable individuals) at Lake Nabugabo, Uganda. We described the patterns of variation in core‐unit associations over time and investigated how changes in rainfall, food availability, and interunit dispersals were correlated with these associations over the short‐term (month to month) and long‐term (year to year).
4. Although clans were relatively stable, larger‐scale changes in association patterns included the formation of an all‐male unit and the transfer of one core unit between clans (within the band tier). Seasonally, core units associated significantly more when fruit, their preferred food source, was abundant (i.e., social networks were denser and more clustered) and there was no direct effect of rainfall seasonality or young leaf availability. Male dispersals also occurred more during periods of high fruit availability, suggesting that greater band cohesion allowed males to prospect and transfer between core units. Once males transferred, their previous and new units associated significantly more with one another than with other core units for 1–2 months postdispersal. The dispersal of five males from one core unit to another in a different clan co‐occurred with this core unit switching its clan affiliation.
5. By examining temporal shifts in social network structure among core units, this study shows the interconnected roles that food availability and dispersal have in shaping the C. a. ruwenzorii multi‐level social system. Our findings highlight how ecological conditions can drive association patterns, impact interunit relationships, and influence social organization.

     

Factors influencing the formation and maintenance of all‐male gorilla groups in captivity

The social housing of males is of particular importance for captive managers of polygynous species. In this work, we highlight nine areas we believe are important to the successful formation and maintenance of all‐male gorilla groups. Although more data are still needed to complete our understanding of these groups, the general picture that emerges is that all‐male groups can be a functional social unit for male gorillas, the longevity of which might be improved by careful planning. It appears that the best time to form all‐male groups is when the animals are still immature, as males in this age class have been observed to form some of the most stable groups. Efforts should be made to diversify the groups in terms of rearing history, particularly with respect to hand‐reared males, and to limit the amount of hand rearing experienced by males. Groups probably should contain no more than three or four adult males. Exhibits should be designed to provide visual barriers, refuges for subordinate animals, the means to separate individuals, and possibly the means to isolate all‐male groups from mixed‐sex groups. Additionally, because it is likely that some males will have to be removed from all‐male groups, zoos need to design facilities that provide state‐of‐the‐art housing for solitary individuals. It is hoped that by identifying bachelor males early in life and establishing cooperative management plans across institutions, zoos will be able to provide beneficial, long‐term social situations for all male gorillas in captivity. Zoo Biol 23:189–203, 2004. © 2004 Wiley‐Liss, Inc.     

Behavior and social structure of the sperm whales of Dominica,West Indies

There is substantial geographic variation in the behavior and social structure of sperm whales worldwide. The population in the Eastern Caribbean is thought to be isolated from other areas in the North Atlantic. We describe the behavior and social structure of the sperm whales identified off Dominica during an eight year study (2005–2012; 92% of photographic identifications) with supplementary data collected from seven other organizations dating as far back as 1981. A total of 419 individuals were identified. Resighting rates (42% of individuals between years) and encounter rates with sperm whale groups (mean = 80.4% of days at sea) among this population were both comparatively high. Group sizes were small (7–9 individuals) and were comprised of just one social unit (mean = 6.76 individuals, SD = 2.80). We described 17 units which have been reidentified off Dominica across 2–27 yr. Mature males are seen regularly off Dominica, but residency in the area lasts only a few days to a few weeks. Males were reidentified across years spanning up to a decade. Management of this population within the multinational Wider Caribbean Region will require governments to work towards international agreements governing sperm whales as a cross‐border species of concern.     

Short‐finned pilot whales (Globicephala macrorhynchus) of the Mariana Archipelago: Individual affiliations,movements, and spatial use

Little is known about short‐finned pilot whales (Globicephala macrorhynchus) in the western North Pacific outside of Japanese coastal waters. To expand understanding of short‐finned pilot whale ecology in the region, we conducted small‐boat surveys in 2010?2016 within the Mariana Archipelago to investigate individual associations, movements, spatial use, and dive behavior of short‐finned pilot whales. We collected genetic, photo‐identification, and satellite‐tag data and identified 191 distinctive individuals. A preliminary social network diagram of photo‐cataloged individuals revealed a main cluster that comprised 82% of individuals, representing all five mitochondrial DNA haplotypes identified within the population. Kernel density estimates for tagged short‐finned pilot whales (n = 11) during summer were used to identify areas with the highest probability of use (10% probability density contour), core area (50%) and home range (95%). The area with highest probability of use by short‐finned pilot whales was off the northwest side of Guam. Satellite tag data also suggest that some individuals are island‐associated year‐round. Data from five location‐dive tags demonstrated that the short‐finned pilot whales dove more often to intermediate depths at twilight and night, suggesting they may target prey that forage on the deep scattering layer as it migrates to and from the surface.     

Individual vocal production in a sperm whale (Physeter macrocephalus) social unit

The vocal repertoires of group‐living animals may communicate individual or group identity. Female and juvenile sperm whales live in long‐term social units that can be assigned to vocal clans based on the pattern of clicks in coda vocalizations. An unusual set of circumstances allowed us to record the vocalizations of photo‐identified individuals within a single social unit over a 41 d period. Using click interpulse intervals, we were able to assign codas to individuals and investigate coda production at the individual level within a social unit for the first time. Adult females in the unit vocalized at approximately equal rates. A calf and juvenile, both male, vocalized less often than the adult females. Repertoires were indistinguishable for all unit members apart from a mother and her calf, which possessed significantly different repertoires—even from one another. We suggest that similarity among the coda repertoires of most unit members indicates a function in advertising unit identity. In contrast, the distinctive repertoires of the calf and its mother may facilitate reunions between these whales. We hypothesize that sperm whales may be able to vary their vocal repertoires as their reproductive status alters the trade‐off between the benefits of individual and group identification.