Actinemys marmorata

Spinks et al. (2010, 2014, 2016) demonstrated deep phylogeographic divergence within the genus Actinemys, corresponding to the previously recognized subspecies, and recommended species recognition for A. pallida (Crother et al. 2017).

Although widespread and with many occurrences throughout its range, this species is highly threatened by invasive predators, lack of reproductive success, droughts brought on by climate change and human water usage, habitat loss, habitat degradation, pathogens, pollution, and direct mortality from vehicles and large machinery. The population has not recovered from steep historical declines that occurred throughout its range due to over-exploitation for the food and pet trades, habitat loss, and the aforementioned list of threats. One study estimated the probability of extinction by 2100 is 50%.

This species occurs in northwestern United States, ranging from Puget Sound, Washington southward with a coastal (western) southern limit at the north end of San Francisco Bay, California and an interior (eastern) southern limit that extends down the west side of the Sierra Nevada (Bury and Germano 2008, Ernst and Lovich 2009, Spinks et al. 2014). A disjunct population in western Nevada has long been suspected of being introduced, although there are fossil records and a potential migration route has been proposed (Bury 2017). It is presumed extirpated from all historical sites in southern British Columbia, Canada (Ernst and Lovich 2009, Barela and Olson 2014). Using post-2004 (the past 20 years) records within the range of A. marmorata (sensu stricto) from Global Biodiversity Information Facility (2024), range extent was estimated to be 378,896 km² (GeoCat 2024).

This species formerly included a subspecies that is now recognized as a full species, Actinemys pallida, ranging along the Coastal Range south of San Francisco Bay into northern Mexico (Spinks et al. 2014).

Spinks et al. (2014) and Barela and Olson (2014) each showed dozens of sites throughout its range. Manzo et al. (2021) reported 50 populations rangewide. Fulton et al. (2022) estimated 38-53 rural sites in the Sacramento Valley and Sacramento-San Joaquin River Delta. There are two occurrences in Washington (Ernst and Lovich 2009) and at least three occurrences in Nevada (Bury 2017).

This species is threatened by native and invasive predators, upland and aquatic habitat loss due to development and agriculture, drought and hydrologic changes, severe floods, pathogens, pollution, and direct mortality from vehicles and agricultural equipment. Invasive predators, pathogens, and land alteration are the most serious threats to this species (Manzo et al. 2021, Gregory et al. 2024). These threats are projected to continue to cause serious declines through the rest of the 21st century (Gregory et al. 2024). Several invasive species pose a threat throughout its range. Pond sliders (Trachemys scripta) compete for basking sites (Ernst and Lovich 2009, Manzo et al. 2021). Invasive American bullfrogs (Lithobates catesbaei) and largemouth bass (Micropterus salmoides) are predators of hatchling turtles and are suspected of drastically reducing juvenile survival when present (Bury and Germano 2008, Ernst and Lovich 2009, Manzo et al. 2021, Gregory et al. 2024). Nest predation by native predators is also a major threat, particularly near anthropogenic habitats, which has been responsible for very low nest success rates across its range (Bury and Germano 2008, Ernst and Lovich 2009, Davidson and Alvarez 2020). A recently discovered infectious disease, pond turtle shell disease fungus (Emydomyces testavorans), is an emerging threat with yet-unknown consequences (Lambert et al. 2021, Manzo et al. 2021).

Anthropogenic water usage has drastically reduced the number of wetlands, quality of wetlands, and amount of surface water throughout its range (Bury and Germano 2008, Ernst and Lovich 2009). Dams have had a number of impacts on this species. Lower water temperatures as a result of the dam on the Main Fork of the Trinity River in California have diminished growth rate and reproductive success in that population (Bury and Germano 2008, Ashton et al. 2015). The Robert Matthews Dam along the Mad River in California has created a perennial waterway below the dam where turtles have better body condition and greater size than turtles above the dam, but nest success may be lower because of the steep, vegetated banks (Bondi and Marks 2013). There are many populations residing in man-made or man-modified aquatic habitats, but many are lacking a sufficient amount of suitable upland nesting sites (Germano 2010, Germano 2016, Davidson and Alvarez 2020, Germano 2020, Germano 2021, Manzo et al. 2021). Road mortality can be a threat in populated areas and along busy roads in sparsely populated areas, particularly during the nesting season (late April through August) (Ernst and Lovich 2009). Agricultural and forestry machinery can also cause direct mortality of nests, juveniles, and adults (Rosenberg and Swift 2013, Alvarez et al. 2017). Stream maintenance programs, designed to prevent urban flooding, can remove habitat for prey species (Karres 2016). Pollution, including pesticides, PCBs, heavy metals, and incidental spills, is a threat throughout much of the range (Bury and Germano 2008, Ernst and Lovich 2009, Germano 2021).

Excessive harvesting for food and collecting for the pet trade led to drastic historical declines, but these are no longer major threats for this species (Bury and Germano 2008).