{"id":1869,"date":"2021-10-17T22:10:32","date_gmt":"2021-10-17T22:10:32","guid":{"rendered":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/?page_id=1869"},"modified":"2022-02-25T03:15:18","modified_gmt":"2022-02-25T03:15:18","slug":"gray-treefrog-complex","status":"publish","type":"page","link":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/gray-treefrog-complex\/","title":{"rendered":"Gray Treefrog Complex"},"content":{"rendered":"\n

The Quick Summary:<\/strong><\/p>\n\n\n\n

The \u201cGray Treefrog Complex\u201d consists of two species: the gray treefrog, Hyla versicolor<\/em>, and Cope\u2019s gray treefrog, Hyla chrysoscelis<\/em>. These two species are visually indistinguishable from one another and their ranges overlap considerably. In the field, the best way to differentiate the two are by the male\u2019s advertisement (mating) call. Otherwise, they can be separated by performing a cytological and\/or cytogenetic analysis. Therefore, if a sound file of the call(s) (or an actual specimen) does not accompany a report or observation, even though there are clear photos, the best and most accurate identification is \u201cGray Treefrog Complex\u201d.<\/p>\n\n\n\n

Gray treefrog, Hyla versicolor<\/em> information<\/a><\/p>\n\n\n\n

Cope\u2019s gray treefrog, Hyla chrysoscelis<\/em> informat<\/a>ion<\/a><\/p>\n\n\n\n

More Details:<\/strong><\/p>\n\n\n\n

The \u201cGray Treefrog Complex\u201d consists of two species: the gray treefrog, Hyla versicolor<\/em>, and Cope\u2019s gray treefrog, Hyla chrysoscelis<\/em>. Some list Dryophytes<\/em> as the generic name. As there is some debate, I will keep using Hyla<\/em> for now. Common names for H. versicolor<\/em> include gray treefrog, eastern gray treefrog, northern gray treefrog, common gray treefrog, and tetraploid gray treefrog. The currently accepted proper name is gray treefrog, though I typically use the former name eastern gray treefrog to avoid confusion with Cope\u2019s gray treefrog. Common names for H. chrysoscelis<\/em> include Cope\u2019s gray treefrog and southern gray treefrog; the currently accepted proper name is Cope\u2019s gray treefrog.<\/p>\n\n\n\n

Although called \u201cgray\u201d treefrogs, both of these species can quickly change their background coloration from gray to brown to bright green in only a matter of minutes.<\/p>\n\n\n\n

The two species of gray treefrogs are indistinguishable based on external morphology; they are identical in appearance (more on this later). The most readily identifiable characteristic to separate the two species in the field is the male\u2019s advertisement (mating) call.<\/strong> Briefly explained here, H. versicolor<\/em> produces a slower more bird-like trill consisting of ~16 to 34 pulses per second, while H. chrysoscelis<\/em> has a faster, more harsh metallic-like trill consisting of ~34 to 60 pulses per second. Keep in mind that pulse rate varies with temperature which can affect both species (faster\/slower calls due to warmer\/colder weather). After some practice hearing the two species call, one can learn to identify each species even if calling in warmer or colder weather. There are many resources online to listen to the calls of both species.<\/p>\n\n\n\n

Gray treefrog, Hyla versicolor<\/em> calling<\/a><\/p>\n\n\n\n

Cope\u2019s gray treefrog, Hyla chrysosc<\/em>elis calling<\/a><\/p>\n\n\n\n

I\u2019ll also briefly cover the cellular differences as well. Some of these differences have not been tested everywhere in their range. Basically, H. versicolor<\/em> is a tetraploid (four sets of chromosomes), has more and larger red blood cells, and larger toe pad epithelial projections with three or four nucleoli in each cell, and H. chrysoscelis<\/em> is a diploid (two sets of chromosomes), has less and smaller red blood cells, and smaller toe pad epithelial projections with one or two nucleoli in each cell. These characteristics cannot be used to distinguish the two species unless a cytological and\/or cytogenetic analysis is performed, except perhaps using a magnification lens to examine the toe pad epithelial projections, but there are some issues associated with the latter method. None of these characteristics are useful for an identifiable voucher photograph. Therefore, the specific species cannot be determined using typical photographs.<\/p>\n\n\n\n

Other Characteristics:<\/strong><\/p>\n\n\n\n

Some researchers have listed other morphological characteristics such as presence\/absence of a pattern on the back, the intensity of the pattern, whether or not the pattern is outlined in black, pattern and\/or color of the insides of the thighs, smoothness\/roughness of the skin, presence\/absence of a light squarish spot under the eye, etc. to tentatively identify the two species. Additionally, H. versicolor<\/em> usually attains a larger size than H. chrysoscelis<\/em>. There may be correlations and basis for these \u201cmore often\u201d or \u201cless often\u201d characteristics, but the bottom line is that currently none of these morphological characteristics have shown to reliably distinguish these two treefrog species.<\/strong><\/p>\n\n\n\n

Some have listed differences in habitat. Just like with the morphological characteristics above, there may be correlations and preferences, but habitat, arboreality, etc. are not a reliable means of identification as there is too much overlap in both species.<\/p>\n\n\n\n

Some have also listed range as a way to distinguish between the two. In general, the two overlap broadly throughout their entire geographic ranges. While more study is certainly needed, there appear to be large gaps with H. versicolor <\/em>apparently absent from a large portion of the southeastern US where H. chrysoscelis<\/em> is found and a large portion of northeastern US where H. versicolor<\/em> is present but H. chrysoscelis<\/em> appears absent. Therefore, the following applies to the Minnesota, Iowa, Wisconsin area. In Iowa, range is not useful \u2013 both species occur statewide, and there are many places where I have found both species calling from the same wetland. I have also found both species calling from the same wetland in Minnesota as well. In Minnesota, people often use range to try to identify a species. For example, in northeastern Minnesota in the arrowhead region, H. versicolor<\/em> has been documented, but H. chrysoscelis<\/em> has not (yet), so some people identify gray treefrogs from this region as H. versicolor<\/em> based upon range. The reverse is true for western Minnesota. However, climate change, habitat alteration, and other factors may cause gray treefrog ranges to expand into areas where they were previously not documented. For this reason, range alone should not be used to identify the two species.<\/p>\n\n\n\n

iNaturalist \u2013 The Quick Summary:<\/strong><\/p>\n\n\n\n

If you only have a photograph\/image of a gray treefrog, use \u201cGray Tree Frog Complex\u201d as the ID. This option may not automatically show up in your suggested IDs. However, if you start to type in \u201cgray treefrog\u201d, it is usually the first option that appears. A photo\/image cannot be used to identify gray treefrogs to species, and no one can justifiably confirm or \u201cagree\u201d to species with only a photo\/image. If you hear them calling, it\u2019s best to take an audio or video recording. You can attach an audio file to an observation, but currently you cannot attach a video file to an observation. If you took a video, there are programs available to take the audio from a video and you can then post that audio to your observation.<\/p>\n\n\n\n

For photos, you could use a higher taxonomic ID such as \u201cHyline Tree Frogs\u201d or \u201cHolarctic Treefrogs\u201d etc., but if you already know it\u2019s one of the two gray treefrogs, (and there are only two Hyla<\/em> in MN, IA, and WI) then it\u2019s most accurate to use \u201cGray Tree Frog Complex\u201d.<\/p>\n\n\n\n

This page replaces the rather lengthy explanation I used to post on these iNaturalist observations:<\/p>\n\n\n\n

It may be that species, unfortunately there is not enough evidence provided to definitively confirm the identification, which can only be accomplished with a sound file of the advertisement call (and\/or a cytological and\/or cytogenetic analysis). \u201cGray Treefrog Complex\u201d covers both species and is the most accurate ID for these observations.<\/p>\n","protected":false},"excerpt":{"rendered":"

The Quick Summary: The \u201cGray Treefrog Complex\u201d consists of two species: the gray treefrog, Hyla versicolor, and Cope\u2019s gray treefrog, Hyla chrysoscelis. These two species are visually indistinguishable from one another and their ranges overlap considerably. In the field, the best way to differentiate the two are by the male\u2019s advertisement (mating) call. Otherwise, they […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"_links":{"self":[{"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/pages\/1869"}],"collection":[{"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/comments?post=1869"}],"version-history":[{"count":17,"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/pages\/1869\/revisions"}],"predecessor-version":[{"id":1897,"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/pages\/1869\/revisions\/1897"}],"wp:attachment":[{"href":"http:\/\/www.herpnet.net\/Iowa-Herpetology\/wp-json\/wp\/v2\/media?parent=1869"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}