CHANGING SEX RATIOS DUE TO GLOBAL WARMING FOR THE NORTHWEST ATLANTIC LOGGERHEAD SEA TURTLE POPULATION

Marissa B Rykowski; University of Miami; m.rykowski@umiami.edu; Elizabeth A Babcock, William Harford

Global warming could be detrimental to sea turtle populations because sea turtles exhibit temperature-dependent sex determination. With warmer temperatures, egg incubation produces a skew towards a female-biased sex ratio. Previous studies suggest that an increase in females is beneficial as more females lead to more eggs. However, these studies have not incorporated a sex ratio dependency for mating success. I compared two models, one with sex ratio-independent mating success and the other with sex ratio-dependent mating success, to see if there are differences in population growth for the Northwest Atlantic population of loggerhead sea turtles. Sex ratios were calculated based on regional temperature predictions from IPCC’s AR5 representative pathway scenarios (RCPs). An age-structured population dynamics model was used to track cohorts from 2005-2100. Hatchling numbers were calculated with and without dependency on mating success. The sex-ratio independent model showed an increase in population size in all scenarios, with the warmest RCP scenario having the greatest increase. Conversely, the sex-ratio-dependent model showed either a stable or decreasing population size. This shows that sex-ratio-dependent mating success may influence our perception of whether climate change is expected to affect sea turtle population growth trends negatively or positively.

Reptiles and Amphibians III   Student Paper InPerson Presentation

 

INCIPIENT SPECIES OF ELGARIA MULTICARINATA COMPLEX LIVING AT DIFFERENT LATITUDES DISPLAY NEARLY INDISTINGUISHABLE THERMAL BEHAVIOR AND TOLERANCE

An Lyu; California State University, Fresno; annnluuu@mail.fresnostate.edu; Keyanna Pinto, Andy Cabrera, Rory S.Telemeco

Molecular genetic tools are commonly used to explore phylogenetic relationships and identify cryptic species, but they are unable to resolve how species function differently ecologically. To create informed management plans, we need to accurately predict how environmental perturbations will affect different taxa. For Southern Alligator Lizards (Elgaria multicarinata), genetic and morphological data suggest that the species is composed of at least two species-level clades, although this diversity is cryptic and can only be distinguished by molecular analysis. I examined whether the thermalbehavior or thermalsensitivity of two clades of Elgaria multicarinata varied based on their northern or southern latitude distribution. My result supported that the two incipient species are almost ecologically identical, with minor differences in their thermalbehavior and tolerance. Selected body temperatures are lower for lizards with larger mass and there is a trend for the Southern clade selecting lower temperatures. Understanding the subtle nuances of thermalbehavior between subspecies can prove crucial to maintaining these species alongside continued climate change.

Reptiles and Amphibians III   Student Paper InPerson Presentation

 

A REVIEW OF THE HISTORICAL MARKET: EFFECT OF THE WEST COAST COMMERCIAL FISHERY ON WESTERN POND TURTLES (ACTINEMYS MARMORATA AND A. PALLIDA)

Matthew Bettelheim; AECOM; blackfish@nasw.org; Chi–Wah Wong

In the mid to late 1800s and early 1900s, Western Pond Turtles (Actinemys marmorata and A. pallida) were sought after in California as an ingredient in turtle soups and stews. At the height of the commercial terrapin fishery in California in 1895, about 63,000 Western Pond Turtles were reported in the markets, but agency records are sporadic and a full accounting of the market data remains incomplete. The USFWS initiated a review of the status of Western Pond Turtles in 2015 to determine if there is sufficient evidence to warrant their listing as an Endangered or Threatened species. To better understand the magnitude of the commercial terrapin fishery, we reexamined commercial fish landing reports of the USFWS and CDFW and other relevant texts available in digital repositories to determine the Reported (known) market data (262,600 turtles). Then we estimated the Model-fitted (unknown) market data (261,500 turtles) to calculate the overall Estimated market total (524,100 turtles). Calculated scaled estimates suggest as many as a million turtles were captured for human consumption. These numbers demonstrate the magnitude of the historical terrapin fishery and could provide a baseline to inform future listing decisions.

Reptiles and Amphibians III  InPerson Presentation

 

UPLAND HABITAT OCCUPANCY BY NORTHWESTERN AND SOUTHWESTERN POND TURTLES IN CENTRAL CALIFORNIA

Jeff Alvarez; The Wildlife Project; jeff@thewildlifeproject.com; , Jeff A Alvarez

Northwestern and southwestern pond turtles are declining throughout their range. Their precipitous decline is correlated with habitat conversion, degradation, and destruction, typically related to anthropogenic sources. Pond turtles of both species utilize uplands for numerous aspects of their natural history and can be found in upland areas for the vast majority of the year. This poses significant concerns for their conservation since locating them in uplands is challenging, to say the least. Knowing which life stages use uplands during specific times of the year can facilitate avoiding injury and mortality, which is critical to sustaining populations of these long-lived species.

Reptiles and Amphibians III  InPerson Presentation

 

RESILIENCY OF THE SOUTHWESTERN POND TURTLE (ACTINEMYS PALLIDA) AFTER DROUGHT IN SOUTHERN CALIFORNIA

Barry Nerhus; bnerhus@endemicenvironmental.net; Lyell Buttermore, Hannah Lee, Lyell S Buttermore

Southwestern pond turtle (Actinemys pallida) populations have been consistently declining throughout their range. This growing concern for population decline is exacerbated by increasing drought, urbanization, and fragmentation. Despite this, focused studies at the San Joaquin Marsh in Orange County, California have demonstrated continuous population growth and stability in the past ten years. We hypothesized that southwestern pond turtle populations at the San Joaquin Marsh demonstrate population stability and resilience despite two years of drought-like conditions. We analyzed the population demographics to determine impacts on population stability in the context of drought. We conducted a mark-recapture survey study over two years (2019-2020) at the San Joaquin Marsh that was then compared to previous pre-drought data (2008-2012). We found that the population estimate at this location had significantly increased in comparison to the previous status reports, even in the face of drought-like conditions. However, we also observed lower juvenile recruitment and a lower proportion of females in reference to males when compared to the previous study conducted prior to drought conditions. Our results indicate a need for conservation and water system management for southwestern pond turtles and further investigation into the status of pond turtle populations, especially after stochastic disturbance events.

Reptiles and Amphibians III  InPerson Presentation

 

POPULATION DYNAMICS OF A SOUTHWESTERN POND TURTLE POPULATION IN ORANGE COUNTY

Barry S Nerhus; Endemic Environmental Services inc; bnerhus@endemicenvironmental.net; Lyell Buttermore

Southwestern pond turtles (Actinemys pallida) have declined throughout Orange County over the past century. Aliso Creek is thought to have one of the largest remaining southwestern pond turtle populations in Orange County. Over 3 years, we investigated a population of southwestern pond turtles to assess the demographics, including population size, sex ratio, and recruitment. We estimate that over 100 southwestern pond turtles reside within the investigated portion of Aliso Creek. This study occurred after of a large arundo removal project in the creek. Further investigation is needed to understand the effects of arundo removal on pond turtle population recovery.

Reptiles and Amphibians III  InPerson Presentation