Ten Years after a Major Riverine Oil Spill: Demographic Effects on a Freshwater Turtle Population

Otten, Joshua G.; Williams, Lisa; Refsnider, Jeanine M.

doi:10.2139/ssrn.4193549

Cited by 3 publications

(14 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, the positive correlation between annual survival and body size we demonstrate here may instead be related to a decrease in predation as turtle size increases; however, adult females travel overland annually to reach nest sites, often 50-125 m from the river, increasing potential for predation or injury due to anthropogenic disturbance (Otten 2022). Although accurate age determination can be difficult because growth rates slow in large adult females, we did not observe a difference in annual survival between size classes ≥18 cm SCL (~15 years of age).…”

Section: Discussionmentioning

confidence: 78%

“…We used the calculated probability of survival, combined with an estimated population size based on empirical data, to conduct sensitivity and elasticity analysis to understand how the study population may respond to events such as widespread adult mortality, a head-start program to increase juvenile recruitment, or nest protection to increase neonate survival. For elasticity and sensitivity analysis, we built a 5-stage age class Lefkovitch matrix model (Figure 2; Caswell 2001) using fecundity (i.e., mean annual female production) and survival probability calculated from the nest and mark-recapture datasets, and the estimated abundances of each age class from Otten (2022). We created our Lefkovitch matrix model under the following assumptions: only females were included, our estimates of fecundity and survival would not change over time, and fecundity and survival depend only on the age class an individual is in.…”

Section: Elasticity and Sensitivity Analysismentioning

confidence: 99%

See 1 more Smart Citation

Bigger is better: age class‐specific survival rates in long‐lived turtles increase with size

Otten,

Refsnider

2024

J Wildl Manag

View full text Add to dashboard Cite

Vital rates for small, non‐breeding individuals are important components of population dynamics for many species, but often individuals of these sizes are difficult to locate, capture, and track. As such, biologists frequently lack reliable estimates of juvenile survival because sample sizes and recapture rates for this life stage are low. Long‐lived animals often take many years to reach sexual maturity and spend much of this time in the smaller size classes, making them sensitive to changes in survival rates. We estimated the survival rates of all size classes for the northern map turtle (Graptemys geographica) using a mark‐recapture dataset with >3,500 captures from 2019–2021 and 210 nests from 2018–2021. As turtle size increased, annual survival probability increased regardless of sex. Estimated annual survival probability for turtles >18 cm long (i.e., adult females >15 years) was about 0.95, over 4 times higher than turtles that were 3 cm long (i.e., hatchlings <1 year; 0.22 annual survival probability). Although we did not observe a difference in survival probability between sexes of any size class, adult females are nearly twice the size of adult males, leading to an increased annual survival probability for females of 0.95, compared to 0.80 for males. Changes in adult survival had the greatest influence on population estimates over time, with temporary decreases, such as those due to poaching or an environmental disaster, potentially leading to unrecoverable decreases in the overall population size. Our study provides detailed survival rates for all size classes in a long‐lived turtle, which are necessary to assess population stability and can be used to determine the most effective conservation or management practices.

show abstract

Section: Discussionmentioning

confidence: 78%

Section: Elasticity and Sensitivity Analysismentioning

confidence: 99%

Bigger is better: age class‐specific survival rates in long‐lived turtles increase with size

Otten,

Refsnider

2024

J Wildl Manag

View full text Add to dashboard Cite

show abstract

“…Therefore, it is possible that individuals with relatively large home ranges may have actually returned to their original home range following translocation, but if we recaptured them farther from their original capture location than the population mean home range length, we would have classified them as not having homed. We have previously estimated that annual detection rates of both adult females and males in this population are ~66%, and annual mortality rates are <5% for adult females and <10% for adult males (Otten, 2022; Otten et al, 2022). Therefore, these detection rates likely mean that some translocated turtles that returned to their original home range were undetected, and therefore that our estimate of homing is conservative.…”

Section: Discussionmentioning

confidence: 96%

“…For all analyses, we used only individuals that were presumed to have been translocated to an unfamiliar location outside of their original home range. To determine whether an individual had been translocated outside its original home range, we used previously estimated mean stream home range lengths for this population, 2.4 km for males, and 4.6 km for females, based on radio-telemetry locations throughout an entire year (Otten, 2022). In this study, we considered translocation distance to be the distance between an individual's original capture location and its translocation release location (Figure 2).…”

Section: Discussionmentioning

confidence: 99%

“…Finally, as a caveat, we likely underestimated overall homing rate due to undetected mortalities or individual variation in home range size and detection rate. Female stream home range size ranged from 1.1 to 17.5 km, while that of males ranged from 0.5 to 6.4 km (Otten, 2022). Therefore, it is possible that individuals with relatively large home ranges may have actually returned to their original home range following translocation, but if we recaptured them farther from their original capture location than the population mean home range length, we would have classified them as not having homed.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Assessing translocation success and long‐distance homing in riverine turtles 10 years after a freshwater oil spill

Otten

Williams

Refsnider

2023

Conservat Sci and Prac

View full text Add to dashboard Cite

Wildlife translocation is often used as a mitigation strategy for construction projects and other disturbances to habitat. In 2010, one of the largest freshwater oil spills in the United States occurred in the Kalamazoo River in Michigan, when over 3.2 million L of diluted bitumen crude oil impacted nearly 56 km of riverine habitat. During 2010 and 2011 cleanup efforts, 686 northern map turtles (Graptemys geographica) were captured from oil‐impacted stretches of the river, cleaned, rehabilitated, and translocated 2.5–84.3 km from their original capture location. The goal of this translocation effort was to release turtles within the same watershed, but away from ongoing cleanup operations, so individuals could potentially return to their original home range after it had been cleaned of oil and restored. In this study, we evaluated the success of translocation as an emergency mitigation strategy for freshwater turtles by quantifying recapture probability and homing by northern map turtles translocated varying distances from their home ranges. During subsequent years of survey up to 10 years post‐spill, 230 of the translocated turtles were recaptured, of which 104 exhibited homing by returning to their original home ranges. Turtles translocated to sites nearest their original capture location had a higher probability of recapture and homing than those translocated further away. Females had a higher probability of returning to original home ranges than males when translocated greater distances. In addition, four females and one male are known to have traveled >50 km between capture and release locations, which to our knowledge is the greatest travel distance recorded for any freshwater turtle species in the United States. Our results demonstrate that riverine turtles have considerable homing ability when displaced long distances, which has important implications for design and success of translocation projects.

show abstract

Here comes the sun: Thermoregulatory behavior in ectotherms illuminated by light‐level geolocators

Otten,

Clifton,

Becker

et al. 2024

Journal of Zoology

View full text Add to dashboard Cite

Daily activity patterns of free‐ranging wildlife affect a wide range of ecological and physiological processes and, in turn are affected by anthropogenic disturbances to the environment. However, obtaining a continuous record of activity without disturbing wild animals is logistically challenging. We used commercially available, multi‐purpose light‐level geolocator dataloggers to continuously record light environment and time spent out of water during 5‐months (1 May to 9 September 2021) in an ectothermic freshwater turtle species, the northern map turtle (Graptemys geographica). We used these data to compare time of year and sex differences in thermoregulatory behavior in an ectothermic species in its natural habitat. We recorded >500 000 data points from 17 individual turtles (nine males and eight females). We found no differences in the mean light levels, or proportion of time spent out of the water, between males and females. However, there was a significant effect of both time of year and sex by time of year interaction in both light level, proportion of time spent dry, and number of state changes (i.e., shuttling behavior, wet to dry or dry to wet), suggesting that turtles alter their aerial basking behavior over the course of the season and that the changes in patterns of aerial basking behavior differ between the sexes throughout the year. In general, the proportion of time spent dry decreased over the active season, with an increase during the last week of June and the first week of July, while the number of state changes increased in females during late May/early June before decreasing, while males remained relatively constant. These changes may reflect the different energetic demands associated with reproduction between the two sexes. The overall downward trend in aerial basking likely reflects the role of increasing environmental temperatures, particularly water temperature, in the maintenance of body temperature in this largely aquatic species.

show abstract

Ten Years after a Major Riverine Oil Spill: Demographic Effects on a Freshwater Turtle Population

Cited by 3 publications

References 26 publications

Bigger is better: age class‐specific survival rates in long‐lived turtles increase with size

Bigger is better: age class‐specific survival rates in long‐lived turtles increase with size

Assessing translocation success and long‐distance homing in riverine turtles 10 years after a freshwater oil spill

Here comes the sun: Thermoregulatory behavior in ectotherms illuminated by light‐level geolocators

Contact Info

Product

Resources

About