During the entire study, three sightings of dwarf sperm whales occurred, resulting in a mean sighting frequency (sightings per hour of effort) of 0.009 and a mean encounter rate (sightings per monitored km) of 0.001. For all three sightings, proximity to the animals enabled the observers to recognize K. sima’s specific characteristics, and during the first and third sightings, photographs documented their morphology, confirming the species identity.
First sighting
On 2 October 2011 at 06:08, two dwarf sperm whales were observed 30 m from the boat in sunny conditions, moderate cloud coverage (30 %), calm seas (Beaufort ≤ 1), and light wind (Douglas 0–1). The location was just outside the harbour of Itsandra Bay, approximately 600 m off the coast (11°40.157’S, 43°14.852’E), at a depth of 32 m (Fig. 1). The sighting was of two animals, the larger estimated to exceed 2 m in length, and presumed to be an adult accompanied by a smaller animal, either a sub-adult or a small adult. When sighted, the two animals were floating and breathing noiselessly about 5 m away from each other. Approximately 2 min after the initial sighting, both animals made two short dives, disappearing from view and resurfacing, and then disappeared after the third dive. Both animals were photographed (Figs. 2 and 3).
Second sighting
The second sighting occurred on 27 June 2012 at 10:32. The location was 720 m off the coast (11°40.157’S, 43°14.852’E), in water 39 m deep (Fig. 1). Similar to the first sighting, the location was just outside of Itsandra Bay in sunny conditions, moderate cloud coverage (30 %), calm seas (Beaufort 1), and a light breeze (Douglas 1–2). The second sighting was also of two animals. We were underway when one animal surfaced 5 m in front of our boat; we stopped the boat immediately and the animal dived. Then two animals surfaced almost 20 m ahead, and were identified as Kogia. One dived immediately and disappeared, leaving no opportunity to identify it to species level, while the other remained on the surface, floating quietly, allowing time to identify it as a K. sima due to the characteristic profile and dorsal fin shape. It subsequently dived and was not resighted.
Third sighting
The third sighting occurred on 8 August 2013 at 06:22, 6 km off the coast of Itsandra Bay (11° 40.121’S, 43° 12.739’ E), in sunny conditions with low cloud coverage (10 %), calm seas (Beaufort 1) and a light breeze (Douglas 1–2). The water depth for the third sighting was 729 m, much deeper than for the first two sightings (Fig. 1). Both animals were photographed, and observed to be clearly different in size. As with the first sighting, we presume the animals were an adult accompanied by a sub-adult, or a smaller adult. Upon sighting the two animals, we stopped the boat. The two animals dived immediately and surfaced nearly 35 m from the boat, then floated quietly about 3–5 m away from each other for 4 min, and made two short dives. After a third dive they were not seen again (Fig. 4).