Cetacean Social Structure

Vocabulary flashcards covering key terms and concepts related to cetacean social structure from the lecture notes.

Paedomorphosis

Evolutionary retention of juvenile traits into adulthood; in porpoises, truncated ontogeny leads to earlier sexual maturity and greater reproductive potential.

Aggregation

Cetaceans commonly found together due to environmental factors (e.g., feeding or mating); not necessarily actively maintained as a social unit.

Group

A social unit actively maintained by individuals, with benefits from interacting with conspecifics.

Social structure

The pattern of interactions and relationships among individuals within a population.

Interaction

Direct behaviours between individuals; described by content (what) and quality (how).

Relationship

Interactions considered together over time, defined by their content and quality.

Association index

A ratio-based measure derived from observations of co-occurrence used to quantify the strength of social bonds between individuals.

Dendrogram

A tree-like diagram that shows how individuals cluster based on their association indices.

Social network

A graphical representation of individuals as nodes and their social ties as edges to visualize the structure of relationships.

Photo-identification

Technique to identify individual cetaceans using distinctive marks (e.g., dorsal fins, scars, coloration).

Dorsal fin

Back fin used as a key marker in photo-identification.

Fluke

Tail fluke used as an identifying feature in cetaceans.

Baleen whales social structure

Often solitary or with brief, unstructured interactions; mother–calf pairs common; social patterns driven by food availability and low predation.

Toothed whales social structure

Exhibits fission–fusion dynamics and more stable, hierarchical societies; smaller odontocetes show frequent associations, larger species may have matrilineal pods and long-term bonds.

Fission-fusion dynamics

A social pattern where group composition changes over time as individuals associate and disband.

Matrilineal pods

Social units organized along female lineages; stable groups of related females and their offspring.

Bottlenose dolphins (Sarasota/Shark Bay)

Two well-studied populations; open-water groups often 2–15 individuals; coastal populations can reach hundreds.

Alloparental care

Care of an infant by non-parent individuals; can influence social structure; examples include Orcas (post-reproductive females), Sperm whales (calves cared for while mothers feed), and Pilot whales (care by both sexes).

Risso’s dolphins social structure

Stratified community intermediate between fission–fusion and stability; males form stable units, females have stable nurseries, juveniles form bachelor pods.

Long-finned Pilot Whales social units

More stable social structure with units averaging about 7 individuals; units interact as labile groups; typical group size around 57–62; matrilines not identifiable.

Philopatry

Tendency of individuals to remain in or return to their natal area; often associated with closed populations.

Demography and social structure

Social structure is influenced by and influences demographic factors (population size, age structure), genetic population structure, population biology, culture, kinship patterns, and fitness.