Marie C. Hill

Dwarf sperm whale (Kogia sima) echolocation clicks from Guam (Western North Pacific Ocean)

The cryptic species of the genus Kogia, including the dwarf sperm whale (Kogia sima) and the pygmy sperm whale (Kogia breviceps), are very difficult to observe in any but the most calm sea conditions. However, recordings of signals from wild and captive animals reveal that they echolocate at high frequencies (peak frequencies > 100 kHz) which makes passive acoustic monitoring (PAM) a possibility. We present details from a recent encounter with K. sima in the wild near the island of Guam (Western North Pacific Ocean). Three individuals were observed during a small-boat, visual survey in May 2016, and recordings were collected using a Compact Acoustic Recording Buoy (CARB). These clicks, with mean peak frequency of 126 kHz ( + /- 4.3 kHz), mean click duration of 72 us ( + /- 21 us), and -3 dB bandwidth 5.5 kHz ( + /- 1.6 kHz), had similar properties to recordings of wild K. sima from the Bahamas (Atlantic Ocean), and also appear similar to published recordings from K. breviceps (Madsen et al. 2005). Availab...

Cetacean Monitoring in the Mariana Islands Range Complex, 2014

We used mitochondrial sequence and nuclear microsatellite loci to examine introgression of Fraser’s dolphin DNA into the Mariana Islands population of bottlenose dolphins. By comparing the nuclear genotypes of the Mariana Islands samples to those of ‘pure’ bottlenose dolphins and Fraser’s dolphins, we estimate that the Mariana Islands animals derive approximately 14% of their nuclear ancestry from Fraser’s dolphins. The fact that every Mariana Islands sample showed evidence of nuclear introgression, combined with the fact that those exhibiting mitochondrial introgression all share the same Fraser’s dolphin haplotype, suggests that there was a single hybridization event far enough in the past to allow Fraser’s dolphin nuclear DNA to permeate the population. The Mariana Islands samples exhibited low genetic diversity compared to other bottlenose dolphin populations, suggesting that they represent a small, genetically isolated population.