Category Archives: science

Should we stay or should we go?

Adult green turtles really like to spend time at the Virgin Islands, and why not? There’s sun, clear water, nesting beaches and seagrass.


Photo: By P.Lindgren – Own work, CC BY-SA 3.0,

We tagged some of the nesting females on Buck Island, a small island off the bigger island of St. Croix. These satellite-tags beamed location data to space and then back to our computers, where we saw that some of these turtles migrated away after nesting – in typical sea turtle fashion – and some stuck around. In fact, 7 of the 10 we tagged stayed in shallow, near-shore waters around St. Croix and Buck Island, while only 3 made long-distance migrations.

This was the first time green turtles from this area (considered a unique management unit) were shown to have this limited migration. It’s important for natural resource managers in the area to know about these movements – or lack thereof – so they can effectively design their management strategies.

So why do some stay and some go? Well, what do you think?

Check out the full article below:

Hart KM, AR Iverson, AM Benscoter, I Fujisaki, MS Cherkiss, C Pollock, I Lundgren, Z Hillis-Starr. 2017.  Resident areas and migrations of female green turtles nesting at Buck Island Reef National Monument, St. Croix, U.S. Virgin Islands. Endangered Species Research 32:89-101. doi: 10.3354/esr00793

Growing turtles need their rest – new paper published


Photo from Wikipedia

We have a new paper out, published in Endangered Species Research, on juvenile green turtles from Dry Tortugas National Park.

Using accelerometers, we assessed both depth and ‘overall dynamic body acceleration’ for the turtles. These two factors showed activity during the day and resting at night, whether or not the turtles stayed in shallow water or traveled to deeper water.

From this, it appeared that traveling to deeper waters at night (as some turtles did) was all about resting. So why do some turtles rest in shallow water and some in deep? Well, it turns out the turtles resting in deeper water got more bang for their buck – they were able to get longer resting dives.

Living in an underwater world means considering sleep differently than you or I might. They need to balance out their bouyancy, which changes depending on how much air is taken in. A larger animal can take a larger breath to fill larger lungs, which mean the animal must go deeper to reach neutral buoyancy. Once there, they can rest longer with all that oxygen stored up.

As a growing young turtle, rest is important. It seems that as they get larger, these turtles are willing to expend more energy to travel to deeper waters AND face potential risks associated with that – sharks are in the area for example – in order to get better sleep.

Read the article online for more.

The full citation is:

Hart KM, White CF, Iverson AR, Whitney N (2016) Trading shallow safety for deep sleep: juvenile green turtles select deeper resting sites as they grow. Endangered Species Research 31: 61-73.

Sonoma County Wildlife website launch!



I am really excited about the launch of a new website that I co-created!

The idea of the website was to create a central place for the Sonoma County community to share knowledge about our wildlife neighbors. We hope to connect county residents to the landscape around them, educate about the wildlife that coexists with them, offer opportunities to get involved in wildlife projects, and inform about local wildlife conservation issues.

I will be writing and editing for the site and hope that it will be a useful tool for the people of Sonoma County. Please go and check it out at!

Sleep deprivation, hawksbills that like variety, and green sea turtles hanging out together

Three new publications out!

First, Guru Magazine has published my article, “Light Sleepers: Why you need to get your sleep, and your light,” about something on my mind a lot during the first year with my new daughter: sleep deprivation. I go over why it’s so important to get those Zzzs (unless of course you LIKE hallucinating and walking into walls, in which case, don’t bother with this article).

The next two were articles published in scientific journals.  “Habitat selection by green turtles in a spatially heterogeneous benthic landscape in Dry Tortugas National Park, Florida” was published in Aquatic Biology. This one is interesting because it mixes two telemetry methods: satellite tracking and acoustic receivers. With these methods, we look at what areas turtles prefer and get clues as to whether turtles spent time with (or avoided) each other. Acoustic data in particular can be tricky to work with, and this paper offers up some ways of working with it.

Hawksbill satellite-tracking case study: implications for remigration interval and population estimates” was published in Marine Turtle Newsletter. I am extra excited about this one because I was first author. In this paper, we talk about Shuli, a hawksbill turtle tagged in the US Virgin Islands . After nesting there, she migrated all the way to the Bahamas before returning to nest again. What was interesting about Shuli was that she nested on a different beach upon her return. In the paper, we talk about how this has implications on counting turtles to get population sizes and also on our understanding of how often individuals nest.

Read one, read all. Learn a little about yourself, learn a little about the natural world.

How the most endangered sea turtle likes to travel

Kemp’s ridleys are the most endangered sea turtle species in the world.


Before conservation efforts, Kemp’s ridleys nested mainly on one 16-mile stretch of beach near Rancho Nuevo, Mexico. A film taken there in the 1940s showed around 40,000 individuals of the species partaking in group nesting, called an “arribada.” Unfortunately, this important nesting beach became a target for massive over-harvesting of eggs and their numbers plummeted shortly after the 1940s film. While it may have seemed to the harvesters that the population was impossible to harm due to its considerable size, the ocean is a dangerous place for hatchlings and chances of survival are slim. It can take hundreds of eggs to produce only one nesting adult, so every egg counts.

The Mexican government attempted to battle the declines by protecting the nesting beach starting in the mid-1960s but the number of nesters continued to drop. Ground-breaking conservation efforts in the late 1970’s between Mexico and the U.S. were taken to try to prevent total extinction of the species – scientists transported eggs from Rancho Nuevo to a protected beach in Texas. At that point the population was reaching critically low levels and on the brink of extinction. Less than 800 nests a year were estimated in the 1980s, accounting for only about 300 nesting females.

Further conservation laws established in the 1990s required an escape route for turtles caught in trawling nets (named Turtle Exclusion Devices; TEDs) in both U.S. and Mexican waters. These devices prevented accidental deaths during fishery operations, although compliance has not been consistent in either country. All of these conservation efforts eventually paid off, and in recent years numbers of nesters began to recover in Mexico (around 13,000 nests counted in 2010) and increase in Texas (around 150 nests in 2010), resulting in over one million hatchlings in 2010.

However, there are other threats in the Gulf of Mexico and its nesting beaches, from too much beach lighting at night to the Deepwater Horizon oil spill in 2010. Whatever the cause, Kemp’s ridley nest numbers decreased during 2013 and 2014 to a 7–8 year low.

In addition to being the rarest, Kemp’s ridleys are also the smallest sea turtle. While the shell of the largest sea turtle species, the leatherback, can measure up to 8 feet in length (they can weight up to 2,000 pounds!), Kemp’s ridleys only reach a little over 2 feet long (and weigh more like 100 pounds).

In a previous paper we looked at the foraging areas that Kemp’s ridleys use in the Gulf of Mexico. Next, we were interested in the areas they migrate through. Migration corridors are important because turtles need to swim through these waters to get to food (foraging area) or nesting grounds. With so many threats in the Gulf of Mexico, we wanted to define these migration areas to help with conservation efforts for these small sea turtles.

Our paper was published in Biological Conservation and you can read it here.