Barren beaches may help nesting sea turtles

Boca’s beaches may be closed to bathers, but nesting sea turtles get a pass. Gumbo Limbo Nature Center is shut too in this emergency. But seven weeks into turtle nesting season, marine conservationist Dr. Kirt Rusenko is out on the beaches doing his count daily. Here’s what he’s finding in this coronavirus beach ban.

Q: Sea turtle nesting season is March 1 through Oct. 31. How many nests are you already seeing on Boca’s beaches?

A: So far, we only have two leatherback nests, no loggerhead or green nests yet. It is still early in the season.  We expect the loggerheads to start showing up maybe next week.

Q: When did you start monitoring and how often do you go out there for a count?

A: We started monitoring the beach mid-February after we heard of nesting leatherbacks in Martin and St. Lucie counties starting Feb. 6.  That was the earliest recorded leatherback nest in Florida. The previous record was Feb. 12.  Since mid-February, we monitor the entire 5 miles of Boca Raton beaches every morning at sunrise.  We also perform monthly lighting surveys at night.

Q: Is this beach ban for people actually better for sea turtles since they can dig nests undisturbed?

A: We assume that fewer people on the beach at night will result in fewer sea turtle “false crawls” or non-nesting emergence.  In areas of undeveloped beach, the nest to false crawl ratio is closer to one to one, which is considered the ideal ratio for loggerheads.  On developed beaches, the false crawl to nest ratio may be as high as two to one (two false crawls for every nest).  Since we have data going back to the early 1980s, we will definitely compare our false crawl to nest ratio while the beaches are closed, to earlier years.  Nesting female sea turtles are generally very cautious and can easily be scared back into the ocean by people on the beach before laying eggs.  There are also other factors such as bad lighting which can cause a sea turtle to avoid that area entirely.

Q: Will condo and A1A lighting laws have any effect on this situation?

A: The local lighting ordinances will still be in effect. The streetlights in the northern mile and a half of Boca Raton went off on March 1 as programmed.

Q: Compared to other years, what are you seeing?

A: It is still too early in the season. Two leatherback nests is about average for us; the first nest was laid Feb. 23.  Loggerheads generally do not start nesting until late April and they really start coming in heavy in May.  Only southeast Florida has the March 1 start of nesting season because we regularly get leatherback nesting in this area.  Greens generally do not start nesting until late May or early June.

Q: Can you explain how these turtles return to the same beach?

A: Sea turtles can navigate with the help of the magnetic fields of the earth.  This ability to navigate apparently develops while the sea turtle embryos develop in the egg. So, when they hatch and emerge from the nest, their compass is already set for the location of the nest.  In general, it appears that loggerheads return to within a few miles of where they hatched.  Greens appear to be slightly more accurate.

By Marci Shatzman


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