Between a Rock and a Hard Place: Habitat Selection in Female-Calf Humpback Whale (Megaptera novaeangliae) Pairs on the Hawaiian Breeding Grounds

Abstract

The Au'au Channel between the islands of Maui and Lanai, Hawaii comprises critical breeding habitat for humpback whales (Megaptera novaeangliae) of the Central North Pacific stock. However, like many regions where marine mega-fauna gather, these waters are also the focus of a flourishing local eco-tourism and whale watching industry. Our aim was to establish current trends in habitat preference in female-calf humpback whale pairs within this region, focusing specifically on the busy, eastern portions of the channel. We used an equally-spaced zigzag transect survey design, compiled our results in a GIS model to identify spatial trends and calculated Neu's Indices to quantify levels of habitat use. Our study revealed that while mysticete female-calf pairs on breeding grounds typically favor shallow, inshore waters, female-calf pairs in the Au'au Channel avoided shallow waters (<20 m) and regions within 2 km of the shoreline. Preferred regions for female-calf pairs comprised water depths between 40–60 m, regions of rugged bottom topography and regions that lay between 4 and 6 km from a small boat harbor (Lahaina Harbor) that fell within the study area. In contrast to other humpback whale breeding grounds, there was only minimal evidence of typical patterns of stratification or segregation according to group composition. A review of habitat use by maternal females across Hawaiian waters indicates that maternal habitat choice varies between localities within the Hawaiian Islands, suggesting that maternal females alter their use of habitat according to locally varying pressures. This ability to respond to varying environments may be the key that allows wildlife species to persist in regions where human activity and critical habitat overlap.

Influence of environmental parameters on movements and habitat utilization of humpback whales (Megaptera novaeangliae) in the Madagascar breeding ground

“…In particular, it is believed that females with calves tend to prefer shallow waters in protected areas (20 m depth or less) [16,24]. Social groups, as mother–calf pairs, could also show a flexible response and adopt alternative behavioural strategies according to abiotic features of regions and the potential human disturbance [25]. Typically, humpback whales are found within close proximity to the coast during the breeding period.…”

Southeastern Pacific humpback whales (Megaptera novaeangliae) and their breeding grounds: Distribution and habitat preference of singers and social groups off the coast of Ecuador

“…We used confidence intervals (95% CI) to determine whether whales exhibited “no preference” (the expected value was above the confidence intervals), “neutral” (the expected value was inside the confidence intervals), or “preference” (the expected value was below the confidence intervals) (see Cartwright et al . , Guidino et al . ).…”

“…, Cartwright et al . ). Shallow water may overlay other factors such as seafloor composition; for example, singers in the West Indies are more often encountered over smooth substrates than any other substrate type (Whitehead and Moore ).…”

“…, ; Cartwright et al . ). For example, in Brazil, Ecuador, and Hawaii, mother‐calf pairs commonly prefer shallower waters less than 20 m in depth (Smultea , Martins et al .…”

“…, Cartwright et al . ). Here, we investigate the spatial distribution, habitat preference and social stratification of singers (using high quality song) and other whale groups within a western South American breeding ground (Ecuador) that is at risk from expanding port activities and tourism.…”