Jeff A. Alvarez | Search USGS

USGS2025

The Southwestern Pond Turtle (Actinemys pallida) in Baja California, Mexico: New localities and persistent threats

The Southwestern Pond Turtle ( Actinemys pallida ), the only native freshwater turtle in Baja California, is experiencing alarming population declines, echoing global patterns observed in freshwater turtles. We conducted comprehensive field surveys across the major drainages of northwestern Baja California to delineate the species' current distribution, identify critical threats to its persistence, and provide guidance for conservation actions. We documented the continued presence of A. pallida at 27 sites across 10 watersheds, ranging from sea level to 1,525 m in elevation. These include nine historically known sites and 18 newly recorded localities. The most pervasive threats we identified were habitat degradation, the proliferation of invasive aquatic species, and unsustainable water extraction. Despite these pressures, our findings confirm that A. pallida still occupies much of its historical range. However, urgent ecological research is needed to inform evidence-based strategies that ensure the long-term viability of this imperiled species.

Baja California↗

USGS2013

Comparative microhabitat characteristics at oviposition sites of the California red-legged frog ( Rana draytonii )

We studied the microhabitat characteristics of 747 egg masses of the federally-threatened Rana draytonii (California red-legged frog) at eight sites in California. our study showed that a broad range of aquatic habitats are utilized by ovipositing R. draytonii , including sites with perennial and ephemeral water sources, natural and constructed wetlands, lentic and lotic hydrology, and sites surrounded by protected lands and nested within modified urban areas. We recorded 45 different egg mass attachment types, although the use of only a few types was common at each site. These attachment types ranged from branches and roots of riparian trees, emergent and submergent wetland vegetation, flooded upland grassland/ruderal vegetation, and debris. eggs were deposited in relatively shallow water (mean 39.7 cm) when compared to maximum site depths. We found that most frogs in artificial pond, natural creek, and artificial channel habitats deposited egg masses within one meter of the shore, while egg masses in a seasonal marsh averaged 27.3 m from the shore due to extensive emergent vegetation. Rana draytonii appeared to delay breeding in lotic habitats and in more inland sites compared to lentic habitats and coastal sites. eggs occurred as early as mid-december at a coastal artificial pond and as late as mid-April in an inland natural creek. We speculate that this delay in breeding may represent a method of avoiding high-flow events and/or freezing temperatures. Understanding the factors related to the reproductive needs of this species can contribute to creating, managing, or preserving appropriate habitat, and promoting species recovery.

Herpetological Conservation and Biology↗