Abstract
Information on site fidelity and ranging patterns of wild animals is critical to understand how they use their environment and guide conservation and management strategies. Delphinids show a wide variety of site fidelity and ranging patterns. Between September 2013 and October 2015, we used boat‐based surveys, photographic identification, biopsy sampling, clustering analysis, and geographic information systems to determine the site‐fidelity patterns and representative ranges of southern Australian bottlenose dolphins (Tursiops cf. australis) inhabiting the inner area of Coffin Bay, a highly productive inverse estuary located within Thorny Passage Marine Park, South Australia. Agglomerative hierarchical clustering (AHC) of individuals’ site‐fidelity index and sighting rates indicated that the majority of dolphins within the inner area of Coffin Bay are “regular residents” (n = 125), followed by “occasional residents” (n = 28), and “occasional visitors” (n = 26). The low standard distance deviation indicated that resident dolphins remained close to their main center of use (range = 0.7–4.7 km, X ± SD = 2.3 ± 0.9 km). Representative ranges of resident dolphins were small (range = 3.9–33.5 km2, X ± SD = 15.2 ± 6.8 km2), with no significant differences between males and females (Kruskal–Wallis, χ2 = 0.426, p = .808). The representative range of 56% of the resident dolphins was restricted to a particular bay within the study area. The strong site fidelity and restricted ranging patterns among individuals could be linked to the high population density of this species in the inner area of Coffin Bay, coupled with differences in social structure and feeding habits. Our results emphasize the importance of productive habitats as a major factor driving site fidelity and restricted movement patterns in highly mobile marine mammals and the high conservation value of the inner area of Coffin Bay for southern Australian bottlenose dolphins.
Highlights
Movement and space use patterns of individual animals affect population distribution and abundance, habitat selection, species interactions, and social and population structure, which in turn influence individuals’ fitness (Börger, 2016; Nathan et al, 2008)
Given the high density of dolphins inhabiting the inner area (1.57–1.70 individuals/km2), their low temporary emigration rates (0.02; 95% CI: 0.01–0.11, Passadore et al, 2017), and the higher survey effort in the inner area compared to the outer area (Table 1; Figure S1), we focused our spatial analyses of site fidelity and ranging patterns on individuals identified in the inner area of Coffin Bay
Marine mammal site fidelity and ranging patterns can provide important information about the space use patterns and relative significance of particular areas to individuals, groups, and populations which are relevant for delineating conservation and management strategies for at-risk species
Summary
Movement and space use patterns of individual animals affect population distribution and abundance, habitat selection, species interactions, and social and population structure, which in turn influence individuals’ fitness (Börger, 2016; Nathan et al, 2008). Some individuals may occupy large ranges while others are restricted to smaller areas; some display year-round residency patterns while others are seasonal or transient visitors (e.g., Connor, Wells, Mann, & Read, 2000; Hunt et al, 2017; McGuire & Henningsen, 2007; Parra, Corkeron, & Marsh, 2006; Silva et al, 2008; Zanardo, Parra, & Möller, 2016) This variety of site fidelity and ranging patterns is thought to be mainly linked to the spatial and temporal predictability of available food resources (Gowans, Würsig, & Karczmarski, 2008).
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