The Pacific tree frog (Pseudacris regilla), also known as the Pacific chorus frog, has a range spanning the Pacific Northwest, from Northern California, Oregon, and Washington to British Columbia in Canada and extreme southern Alaska. They live from sea level to more than 10,000 feet in many types of habitats, reproducing in aquatic settings. They occur in shades of greens or browns and can change colors over periods of hours and weeks. Taxonomy The taxonomy of this frog has a very confusing history. First, the frog was moved from the genus Hyla to the genus Pseudacris in 1986, and Hyliola in 2016 (an elevation of the subgenus which has not been widely accepted). In 2006, Recuero et al. split the frog into three species based on DNA evidence. Recuero et al. used incorrect names for two of the three populations, but subsequent authors established that the correct name (i.e., the oldest available name) for the northern component is Pseudacris regilla, for the central one Pseudacris sierra, and for the southern one Pseudacris hypochondriaca. This revision has been controversial but the evidence is supported by other research (e.g., ), and is followed in this article. Anatomy and morphology The Pacific tree frog grows up to 2 inches from snout to urostyle. The males are usually smaller than the females and have a dark patch on their throats. The dark patch is the vocal sac, which stretches out when the male is calling. Pacific tree frogs can be a number of different colors, including green, tan, reddish, gray, brown, cream, and black, but most are a shade of green or brown, with pale or white bellies. They have a variety of dark and spotty markings on their backs and sides and can be identified by a black or dark brown eye stripe that stretches from the nose, across the eye, and back to the shoulder. They can change color seasonally to better match their environments. Their skin is covered in small bumps. They have long legs compared to their bodies and they tend to be slender. Their toes are long and only very slightly webbed. On the end of each toe is a round, sticky toe pad or disk used for climbing and sticking to surfaces. Males also have an extra, and far less noticeable toe on their outer thumbs used exclusively in amplexus. Fertilization is external. Distribution, habitat and ecology Pacific