in the dorsal coloration of a color morph can take from weeks to months, but initial changes can occur in just a few hours. This has been shown to be a very useful cryptic survival feature for these frogs. Skin color is produced via pigment cells called chromatophores. Three types of chromatophores are commonly found in amphibians: Xanthophores, which contain yellow, orange, or red pigments and are found uppermost on the dermis; iridophores, which lie below the xanthophores and function by reflecting and scattering white light up through them (in the case of Pseudacris regilla and many other North American frogs, iridophores reflect blue light through the yellow pigment cells above to create a green frog) and melanophores, which are the deepest pigment cells and are responsible for the presence of black and brown pigments. A rare, recessive "blue morph" is known. One is housed at the Humboldt State University Natural History Museum in Arcata, California. This mutation might inhibit the xanthophores' ability to produce yellow pigments, thus the normally green frog (possibly of the color-unchanging type) appears blue. Homing Research was done on Pacific tree frogs to discover if they have homing instincts and what was their main source for knowing where their home was. To find the answer, these frogs were marked and moved 300 yards away from their pond. Several days later, the researchers did a recapture on the original pond in which 66.3% of the frogs were recaptured, indicating there was some source of homing instinct. This was made apparent again when 24 frogs were placed into a larger pond, and 20 of those frogs returned to their original pond. The frogs' movement patterns and olfactory, auditory, and kinesthetic senses could be explanations for the homing, but not a single factor was able to explain the results, indicating that these frogs might be using all or a combination of these factors for homing. Conservation status These frogs (if one includes the two very closely related species, as discussed above) are the most common frogs on the West Coast of North America. Although Pacific tree frogs remain abundant, some other species found in the same areas, such as California red-legged frogs, are declining. Most populations of tree frogs appear healthy, and they have no concern or conservation status. Regional importance In 2007, the Pacific tree frog was named the state amphibian of the State of Washington. It