Field research for the 2019 season concluded in December and will resume again in May 2020. In the meantime- read about our recent publications!
Why Do Dolphins Sponge?
The Shark Bay dolphins have long been renowned for their use of marine sponges as tools. Previous research has demonstrated that dolphin mothers’ pass the tradition of sponge use down to their daughters and some sons, and three generations of spongers have been observed so far.
However researchers are just beginning to understand why this rare example of tool use by cetaceans has developed and persisted in this population.
In a new paper in PLoS One researchers show that dolphins use these tools both for protection while ferreting out prey from the rocky seafloor, but also to allow them to hunt bottom-dwelling fish that lack swimbladders, which are undetectable by the traditional methods of vision and echolocation.
The authors suggest that this method allows the Shark Bay dolphins to take advantage of this ecological niche that is otherwise unavailable without the use of tools. Check out our Videos Page to see a demonstration of sponging in Shark Bay!
The Blow Project
Celine Frère, Ewa Krzyszczyk, Janet Mann & Eric Patterson
Dolphins obviously come to the surface to breathe and occasionally they blow hard enough when bow-riding our boats that we get sprayed in the face. We have recently decided to capitalize on this by developing a new non-invasive method, “blow-sampling”, which involves collecting fluid exhaled from the blowhole, and will explore the full potential of this biological sample. Our study population is ideal as we have monitored individual life histories, reproduction, behavior, genetics, and ecology for so many dolphins. In addition, the provisioned dolphins that visit Monkey Mia are an ideal population to test our methods. Thus, we can sample blow daily from the same individuals in different reproductive states, with known relatedness and partially controlled diets, allowing us to ground-truth the method and apply it to our population at large. In a 2008 pilot study we collected 90 blow samples from provisioned and non-provisioned dolphins and extracted mtDNA (maternally inherited) from their blow. In 2009 we partnered with the National Aquarium in Baltimore, Maryland, USA so that we could refine our methods. Here the bottlenose dolphins were trained to blow after a light touch on the melon. We collected their blow and successfully extracted DNA. In addition, we were able to match the DNA profiles to blood samples that the Aquarium collects for routine medical procedures. This work has now been published in PLoS One. Next we hope to identify reproductive state through hormones, diet through fatty acids, health through disease presence, and kinship through mtDNA and nuclear DNA in the Shark Bay dolphins. We can then correlate these measures with age, sex, behavior, reproductive patterns and survival. This innovative and non-invasive project will acquire much-needed data for improving dolphin welfare, and can potentially set a new standard for biological sampling of cetaceans.
In addition to several new publications, we have been presenting our work at numerous conferences. Some of these presentations focused on sexual maturation and speckling in dolphins; see grad student Ewa Krzyszczyk’s work below. Others described sponge tool use including the social networks of spongers (Mann et al. 2010), and several presentations (led by Dr. Margaret Stanton) focused on social networks of mothers and calves including on how sociality can affect survival. Researchers from several universities are collaborating to investigate the development of echolocation in newborns. Other new projects are listed below.