A treasure from the past: former sperm whale distribution in Indonesian waters unveiled using distribution models and historical whaling data

Aim: This study is the first in Indonesia to assess historical sperm whale (Physeter macrocephalus) seasonal distributions by combining historical whaling data with environmental factors associated with sperm whale habitat preferences. Since current records of whale occurrence covering the whole of Indonesian waters are incomplete, we used historical whaling data summarized by Charles Haskins Townsend in 1935 to model its potential distribution for each season.

Location: Indonesian waters (92-143E, 9N-14S)

Taxa: Sperm whale (Physeter macrocephalus)

Methods: We used a presence-only habitat model -Maximum Entropy (Maxent)-, and a presence-pseudo-absence method -Generalized Additive Model (GAM)- with nine submerged topographic variables to predict historical seasonal distributions.

Results: Both Maxent and GAM predict similar potential distribution which align closely with the whaling data. The results indicate that in four areas in the eastern part of Indonesia, no seasonal di...