Pilot whale encounters 30 miles offshore

Our Research Team has begun surveying the deeper waters southwest of Maui as part of our new false killer whale study. The first day of research took us ~30 nautical miles off the coast of Maui in waters >2,500 feet. Although we didn’t see any false killer whales, we did have two encounters with short-finned pilot whales, a species we do not typically observe in the near-shore waters of the Maui 4-island region. This species has distinctive bulbous heads, wide dorsal fins, and sleek black bodies. Short-finned pilot whales are sexually dimorphic, which means that males and females look different. Males typically grow to 18 ft long compared to females who grow to an average length of 12 ft. The dorsal fins on males are also larger and wider than females, making it easy to tell the two apart.

During our encounter with short-finned pilot whales, two researchers were taking above water photographs of the whale’s dorsal fins, another researcher was collecting underwater footage using a pole-mounted camera, while a fourth research was collecting detailed observations on pod behavior and composition. We observed two mother-calf pairs, two subadults, and the rest were adults, spread out into smaller sub-groups of 2-3 individuals. During the encounters we observed the pod feeding and resting at the surface of the water.

The majority of our research takes place after our field work ends, because the data we collected in the field must be processed. This involved looking through 520 pictures of dorsal fins, assessing each image’s quality, and matching each image within the encounter to see how many different individuals we saw. After data processing was completed, we had photographically identified 19 different animals. These individuals were then compared to our existing catalog of 133 short-finned pilot whales to see if any have been previously sighted. One individual matched to our catalog and was sighted back in September 2002. The other 18 animals had never been seen before and were added as new individuals, increasing our catalog size to 152 individuals. Since we do not often see this species, it was expected that there would be many new individuals to add, as the estimated population size for the entire Hawaiian Islands EEZ is 12,422 whales (Bradford et al. 2013).

This was a very successful day offshore! Stay tuned for other research updates from this exciting new study.

Seeing Some Familiar Fins

The PWF research team recently had a great encounter with a pod of bottlenose dolphins that were hunting fish. Back in the office, we used the bottlenose dolphin photo-identification catalog to reveal some interesting information about the group. As it turns out, this pod contained an adoption animal (#095, “Pa‘ani”), our oldest cataloged animal (#005), a dolphin newly confirmed as a male (#114), and a female who had a calf last summer (#006).

Dolphin #005 was sighted in the very first pod added to the PWF bottlenose dolphin catalog in 1996, and dolphin #006 was first seen in 1997, making them at least 21 and 20 years old, respectively. Our adoptable female, #095 (“Pa‘ani”), was first seen in 2010, meaning she is potentially a bit younger than #005 and #006. Since she had already reached her adult size when she was first seen, it is difficult to determine her actual age, but we know she is at least 7 years old.

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Sightings of baby spinner and spotted dolphins

Recently the research team set out towards the island of Lanaʻi to continue our odontocete and marine debris surveys. Around 9:30 am, we came across a pod of approximately 100 spinner dolphins, including five calves. Even better, two of the calves were neonates: newborn dolphins!

Neonates can be distinguished by their small size: only 75-80 centimeters long in spinner dolphins — about the length of a skateboard. They also have “fetal folds” on their sides. These vertical, lightly-colored “stripes” are the result of being folded up inside mom, and they fade with time as the calf grows.

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Underwater Footage of Whales and Dolphins Interacting

If two animals share the same environment, then at some point they are likely to meet. In the wild these meetings are often between predator and prey; however, nature isn’t always so cruel. Some such encounters, referred to as “interspecies interactions,” can be playful or social, where neither individual is threatened.

 

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Double Take: False Killer Whales and Pilot Whales in the Same Day

When the research team carries out odontocete transects, we are looking for all species of toothed whales, but most commonly we see bottlenose, spotted and spinner dolphins. On rare occasions we see false killer whales, of which the insular Hawaiian population is on the endangered species list, and short-finned pilot whales, which is a deeper water species not commonly found in the shallower waters of our survey area. We might see these two species a handful of days per year. Well, believe it or not, we were recently lucky enough to see them both on the same day!

We were surveying the area behind the island of Lana‘i and we had a feeling it was going to be a special day when we set off from Ma‘alaea Harbor. We had just arrived at the start of our first transect line when we saw a large black dorsal fin. We soon realized that this was a false killer whale. At first we only saw one solitary individual, but it soon swam and joined the rest of its pod, which we estimated at 15 individuals. We photographed them to obtain ID’s for our false killer whale catalog and collected behavioral data. When we were satisfied that we had photographed all the individuals present we returned to our transect line, excited that we had such an exciting experience so early in the day.

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Mother-Calf Dolphin Resight

On August 12, the research team went out on the water surveying for odontocetes and marine debris. At around 11 am, we sighted a pod of 17 bottlenose dolphins and began taking photographs, as per our protocol. We spent the maximum allowed hour with this pod, giving our interns a chance to try their photo-identification skills and collect as many dorsal fin photographs as possible, as the pod was milling about and not difficult to keep track of. While we were watching the dolphins, we noticed there were two distinct pairings in the pod.

Later that week when we were in the office cataloging and examining the photographs, our analyst Jens noticed that one of the pairs was already in our bottlenose dolphin catalog. The same two individuals had been photographed together as a mother-calf pair  in 2011.

This mother and calf pair was sighted on August 6, 2011 and again on August 12, 2014.

This mother and calf pair was sighted on August 6, 2011 and the pair was seen again on August 12, 2014.

This is pretty neat because using photo-identification we can track how long these two individuals stay together. Bottlenose dolphins have a complex social structure that is very different from odontocetes that live in stable groups like a pod of killer whales. They live in a fission-fusion society, meaning it is dynamic and always changing. However, the association between a mother and calf is one of the strongest bonds in the dolphin society. They will stay together on average for between three and six years, and we know that these two have been together for at least three years. It will be interesting to see what happens to these two individuals in the future.