Sperm whale presence within the Kaikōura Canyon in New Zealand has decreased by nearly 50% within the past 30 years. To investigate this shift in habitat use, Guerra and colleagues measured the presence and absence of whales within this region within generalized additive models (GAM) to investigate presence in relation to the geographic characteristics of the region (depth, slope, aspect).
The probability of sperm whale occurrence was modeled by the best GAM, which was evaluated using multi-fold validation. These models were used to predict the probability of occurrence of whales at any given location within Kaikōura Canyon. Maps were then generated within ArcGIS using the inverse distance weighting to the first power. This was accomplished using the IDW tool in ArcGIS. Bathymetry of the canyon was overlaid on this raster layer to help assess relationships between space and sperm whale occurrence.
The results suggest that sperm whales are highly selective about where they forage. Although foraging areas are highly complex to predict, they can be partially explained by depth, temperature, and other geographic features. This study shows the use of geographic variables and models to predict habitat use which can be used to conserve protected species such as the sperm whale.
Guerra, Marta, et al. “Fine-Scale Habitat Use of Foraging Sperm Whales Is Driven by Seafloor Topography and Water Column Structure.” Marine Mammal Science, vol. 38, no. 2, 2022, pp. 626–52. Wiley Online Library, https://doi.org/10.1111/mms.12881.
