MORE ON THIS: In Hawai‘i, Hawksbill turtles mostly nest on Hawai‘i Island, but Maui is home to some of the nesting beaches for ten of these turtles. Beginning around age 20, a female will return to the area where she was born between May and October every 3 to 9 years to lay her eggs. Hawksbills will nest at night and will lay 2-5 sets of eggs, or clutches, in the same season. Each clutch will be laid approximately 16-23 days apart. To lay eggs, the turtle will haul out onto a beach to find a suitable area, dig a deep pit using her flippers, and then fill the pit with her eggs. A single clutch averages 180 eggs. Once she is done laying her eggs, she will use her flippers to fill the hole in with sand before returning to the sea.
FACT OF THE WEEK: Bottlenose dolphins may address each other by name!
MORE ON THIS: Recent research has suggested that bottlenose dolphins have individually unique signature whistles that are equivalent to human names. During the first few months of life, a dolphin will develop its own signature whistle made up of a series of sounds and notes. Dolphins will also adopt the signature whistle of other dolphins in the pod to identify and communicate with different individuals, specifically close associates or those with strong social bonds. When a dolphin emits its own signature whistle, a dolphin that is a close associate will reply with a copied version of the whistle with a few subtle alterations that differentiates the signature whistle from the copied whistle. This allows the second dolphin to relay information back to the first dolphin; the alterations to the whistle may also give information about who the second dolphin is.
Many species of dolphins live in fission-fusion societies, this means that the size and composition of the pod will change as time passes. When pods merge together, vocal signatures are exchanged in order to learn about the identities of individual members of the new pod. These exchanges are generally repeated several times during the interaction to either improve the probability of correct identification, or provide additional information with each exchange.
- Quick, N.J. and Janik, V.M. 2012. Bottlenose dolphins exchange signature whistles when meeting at sea. Proceedings of the Royal Society B 279 (1738): 2539-2545.
- King, S.L. and Janik, V.M. 2013. Bottlenose dolphins can use learned vocal labels to address each other. Proceedings of the National Academy of Science 110(32):13216–13221.
- King S.L, Sayigh L.S., Wells R.S., Fellner W., and Janik V.M. 2013. Vocal copying of individually distinctive signature whistles in bottlenose dolphins. Proceedings of the Royal Society B 280:1-9.
Written by Patrice Hostetter
FACT OF THE WEEK: The underside of a whale’s tail, called the flukes, is not the only characteristic that can be used to photo-identify baleen whales.
MORE ON THIS: You may already know that humpback whales have individually unique tail flukes, like a human fingerprint, and can be identified by photographing these. In addition, each humpback whale also has a unique dorsal fin that allows researchers to track and study individual whales using photo-identification techniques. But did you know that other species of baleen whales are identified using other body parts?
Gray whales don’t actually have a dorsal fin; instead they have a series of “knuckles” along their back. Researchers can use the shape of these knuckles, as well as mottling, scarring, and barnacle patterns on the whale’s back to identify individuals.
Minke whales are identified using nicks or notches in their dorsal fins, or by unusual dorsal fin shape, similar to photo-identification in dolphins. They can also be identified on the basis of lateral body pigmentation.
FACT OF THE WEEK: Zoonotic disease Brucellosis found shared between marine mammals and humans.
MORE ON THIS: Zoonotic diseases are those which can be passed between humans and animals. Brucella spp. is the genus of bacteria which causes the zoonotic disease Brucellosis, and can be found in numerous domesticated livestock and wild animals. The Brucella strain in domesticated animals has been eradicated in most industrialized countries, but unfortunately, in developing countries, it is still an issue. The disease has also been found in marine mammals, particularly recorded in dolphins, seals and sea lions. Symptoms in each terrestrial or marine mammal vary, and acquiring the disease can be done by ingesting the bacterium or by touching an open wound.
FACT OF THE WEEK: Humpback whales are home to three different species of barnacles and one species of whale lice
MORE ON THIS: The relationship between these barnacles and humpback whales is an example of commensalism, where one species benefits and the other is unaffected. The barnacle benefits from this relationship because it is provided with a place to live and filter food. The whale seems to be not affected by this, and might even benefit as well. Humpback whales have been known to roll over when being attacked, so the predator is faced with a tough surface of barnacles instead of soft skin.
Whale lice are highly specialized – each species of whale has its own unique variety of whale lice. Their name is actually a misnomer, because while they look like human lice, they are actually a type of crustacean called cyamids. The relationship between whales and their lice is another example of commensalism, like barnacles. Whale lice feed on algae and whale skin, but there is no evidence that whale lice are harmful to whales.