Solitary versus group living lifestyles, social group composition and cooperation in otters

Abstract

Increased reproduction success, enhanced foraging and reduced predation risk are usually regarded as major factors favouring the evolution of social behaviour. Here we formulate a series of hypotheses relating sexual, ecological and behavioural factors to evaluate their explanatory value for 13 extant otter species, estimating the extent to which each factor contributes to the sociality of each species. We also compare individual behaviours within some of the species. Four otter species are obligatory social; four are obligatory solitary; five present both types of social organization. Social organizations of otter species are not related to their phylogenetic relationships. However, many otter species exhibit intra-species patterns of flexible social lifestyles. Both solitary and social otters adjust their social patterns in response chiefly to food availability, but also to habitat features and competition.Group living is more common when intraspecific competition is reduced or trophic resources replenish rapidly. Under these circumstances, group members often forage individually. When otters forage individually, they often switch prey type when they compete with other conspecifics. Social structures of otters fall into seven types: (1) family groups; (2) extended family groups, often with an alpha dominant pair; (3) highly social groups with helpers; (4) collective hunting groups; (5) solitary lifestyle; (6) unstable mixed-sex groups; and (7) single-sex bachelor groups. When an individual of a species with variable sociality adopts one type of sociality, this may be only temporary. Variations in social life are actually based on a series of events that induce individuals to make decisions taking ecological factors into account.Although ontogenetic factors can influence delayed dispersal of otters, social factors rather than ecological factors could play an important role in the formation of groups, and cohesiveness and kinship appear to be secondary effects of reduced dispersal more than primary causes for living in a group. Appropriate adjustment of group behaviour reduces the cost of sociality because individuals avoid social interactions when benefits are low but gather together when group living provides real advantages. Although any one model is unlikely to explicate all facets of sociality, evolution towards a social group results mainly from interactions within a family.

Nuevas Observaciones De Lontra Felina (Molina, 1782) en El Litoral De Lima Y Callao, Peru

“…Se avistaron seis nutrias marinas y se hallaron cuatro carcasas de nutria marina en diferentes localidades de la zona de estudio. En la mayor parte de las observaciones se registró a un solo individuo, ya que la especie exhibe hábitos solitarios (Lodé et al, 2021). Adicionalmente se observaron huellas y restos de fecas en cuevas y zonas rocosas localizadas en Punta Matacuatro (11°47'15,697" LS, 77°11'17,759" LW) y alrededores, las cuales están ubicadas al sur de Playa del Club Naval.…”

Population distribution and causes of mortality of smooth-coated otters, Lutrogale perspicillata, in Singapore

“…Smooth-coated otters display flexibility in social structures. The lack of dispersal can be explained as improving survival in poor ecological conditions and social benefits from the acquisition of experience and provision of support in sibling care ( Lodé et al 2021 ). In Singapore, one explanation for the limited dispersal of juveniles could be the lack of unoccupied habitats; the habitat saturation hypothesis suggests juveniles delay dispersal in these scenarios ( Koenig et al 1992 ).…”

“…For example, the Bishan group was dominant in the Central Watershed when Bishan numbers were 13; and Zouk, Singapore Botanic Garden, and Marina group numbers were 11, 7, and 11, respectively. As group-living in otters is promoted by food availability ( Lodé et al 2021 ), the large groups in Singapore at Pulau Ubin, Ulu Pandan, and the Central Watershed indicate that there are abundant, replenishing resources available to host large smooth-coated otter groups within those areas.…”

It's about time: Feeding competition costs of sociality are affected more by temporal characteristics than spatial distribution

“…Gregariousness, the behavioral tendency to tolerate and/or affiliate with conspecifics, can vary from near‐complete avoidance in certain species (e.g., pumas, Elbroch et al., 2017 ), to obligate sociality that creates large permanent groups in others (e.g., female elephants, de Silva & Wittemyer, 2012 ; eusocial insects, Nowak et al., 2010 ), with much variation and flexibility in between (e.g., otters, mice; Lodé et al., 2020 ; Schradin et al., 2020 ). Before considering why groups of a particular size form, which is likely to be influenced by many different factors, it is important to consider from an individual's perspective why an animal would coordinate its movement with conspecifics, i.e., what benefits or costs (or both) an individual faces when tolerating conspecifics nearby (Alexander, 1974 ; Miller, 1922 ).…”