Turtle Hatch Rates Skyrocket after Incubation
This post belongs to a series written by students in the Conservation Biology course BSC4052 at the University of South Florida. This course provides an overview of major themes in conservation practice and related applied problems in biology, including: population ecology in the context of conservation, patterns of diversity, valuing diversity, threats to diversity, management actions and strategies for preserving diversity.
Author: Rebeka De Turo grew up visiting Florida’s beaches and springs with her family, which is where her love of nature started from an early age. She is currently a senior at the University of South Florida pursuing her bachelor’s in Marine Biology with a minor in Deaf Studies. Upon graduation, Rebeka plans to pursue a career in conservation in Florida to help protect the environment that has inspired her so much.
What is happening to the Spiny Softshell Turtles?
The spiny softshell turtle ranges from Mexico to southern Canada (van Dijk, 2011). The Lake Champlain spiny softshell turtle population has recently declined largely due to human activities such as fishing (which leads to entanglement in the gear and decreases the turtles’ food supply) and loss of habitat from flooding associated with climate change and agricultural activities. There is also evidence of intense predation in the area, noticeable by broken eggshells. Low hatching success may also be contributing to the continued decline of this population. A recent study by Louis Lazure and his team investigated nesting biology and the factors that promote high hatching success for the Lake Champlain population of spiny softshell turtles.
Studying 10 years of spiny softshell turtle hatching near Lake Champlain
From 2003 to 2013, Lazure and his team observed the hatching success of twenty-one nests in a tributary off Lake Champlain. The team’s goal was to determine if characteristics of nesting habitats were correlated with hatching success. Initially, hatching rates were low, prompting the team to test whether they could increase the hatching success through various measures. For example, some nests were relocated to a higher elevation to reduce flooding concerns, others were covered with wire mesh to protect it from predators, and the remaining nests were both covered and relocated to higher grounds. Additionally, in 2009 the study authors removed some of the eggs from their natural environment and artificially incubated them in the lab. Similar substrates as the turtle’s natural habitat were used to recreate the nests, such as sand and moss, and the environmental factors (i.e. temperature and humidity levels) were mimicked. Artificial incubation refers to the process of caring for and hatching eggs in a lab.
Did the conservation efforts help with turtle hatching success?
At the end of their study, the researchers compared all the observed nests’ hatching success rates to determine which conservation effort was the most effective. The natural nests that were undisturbed had a success rate of 38% (149/390 eggs), which is a low rate of hatching success, but was within the range of hatching success found in other studies. The nests that were either relocated or protected had a success rate of 0% (0/114 eggs). The researchers found many relocated nests suffered from a lack of moisture, and those protected with wire mesh were safe from predators, but still suffered heavy mortality from flooding as they were laid in a flood zone. The nests that were both relocated and protected with wire mesh had a success rate of 44% (13/32 eggs). But by far, the most successful approach was artificial incubation. Despite the first year not being very successful with 0% hatching success (0/33 eggs), the incubated eggs reached a success rate of 84% (1035/1234 eggs) over the following seven years, more than double the natural success rate!
What does this mean for the future?
While the artificial incubation success rate of 84% is exciting, the goal of conservation is to be as hands-off and self-sustainable as possible. Currently, this goal is not a reality for helping spiny softshell turtle populations recover. There is intense predation in this area, and high river discharge from agricultural fields causing flooding, which both lead to higher risk for egg mortality. To remedy this, Lazure and his team plan to restore nesting habitats by improving shoreline and water quality, as well as reducing other causes of mortality. The team also plans to monitor the survivorship of the population’s adult females and juveniles to determine which age is most crucial in helping this species recover. The team also plans to educate the public on the effects of fishing and habitat degradation in the area. Until all these measures have taken place to help improve hatching success of wild nests, the success of this research team in achieving a high hatching rate through artificial incubation marks an important step to slow down or reverse population declines.
van Dijk, P.P. 2011. Apalone spinifera (errata version published in 2016). The IUCN Red List of Threatened Species 2011: e.T163451A97398618. https://dx.doi.org/10.2305/IUCN.UK.2011-1.RLTS.T163451A5607536.en.