Identifying Virginia's Leopard Frogs

10/7/2020

Southern Leopard Frog that lacks a speck in the tympanum | © Ty Smith

F.Y.I. Kauffeld's Leopard Frogs and Southern Leopard Frogs are quite similar. The general consensus is that they really need to be in hand or heard properly to ID. While this is not always the case, there is tremendous overlap among the two. So, I linked the iNaturalist observation to the photo in all of the Kaufeld's/Southern Leopard Frogs photoed (but the figures) so you can see all angles I captured of each specimen. That way you know I am not "just blowing smoke".

Stop with the SPECK!

Some of the most confusing frogs in Virginia are the Leopard Frog. Phylogeneticists refer to this massive clade of Lithobates species as "Pantherana", and I will today as well. I have to say, I love this name. "Panthera" refers to big cats, like the Leopard which are the genus Panthera, and "rana" refers to frogs, like the genus Rana which used to even contain Leopard Frogs. Whoever came up with this name literally just smacked the words together and called it a day. It works so perfectly! One of my biggest pet-peeves though, is when a field mark that is an "average trait" is published across media as a "key trait". If you don't know what that means, well we have an article that discusses all of that here in great detail.

How does this relate to Leopard Frogs? Well, you may have heard, "Southern Leopard Frogs have a silver/light speck in the center of the tympanum." (I didn't intend to quote anyone directly and if I did it is because this was the way it popped into my head, so if I did directly quote a guide, kindly let me know so I can fix my citation error). While Pickerel Frogs lack this speck, Kauffeld's Leopards often have it (especially on the Eastern Shore, but some coastal plains ones as well), and not all Southern Leopard Frogs have this speck. So, in actuality, a speck just means it is not a Pickerel Frog... How do we identify Pantheranans you ask? You use the "sum of its traits" approach.

Kauffeld's Leopard Frog with a speck in the tympanum | © Ty Smith

Three Frog Night

So, new herpers struggle with Pickerel vs Southern Leopard while your higher levels struggle with Southern vs Kauffeld's Leopard Frog. There are a few herps where we are told, "You can only ID these if you look at _____." My motto is if you only look at that single trait, all you will ever see is that single trait. By doing so, you can see for yourself how similar two species actually are. This is the reason that A.) very few people can identify Plestiodon skinks and B.) many people overlook key differences like size. If all you look at is scale counts that aren't even accurate, how will you ever truly learn how to ID anything. Same with toads. People tell me all the time that they have never noticed the difference in the average sizes, patterns, or head shapes in Fowler's and American Toads until I pointed it out, because they are counting warts. This "silver speck" I mentioned above is the same issue, but in a different species. Generally, after I have looked over a couple specimens of two very similar species, I like to try to predict which is which before looking at the key trait. For example, if I am in a park and see a crow on the wire, I tell Evan, "I bet that is a Fish Crow.", before we even hear it in order to gage how good am I at knit-picking the two based on all features. Then we decide based off of the call; which is generally considered the "only way to be sure". Overall, I am about 4/5 on crows and I do about the same for Kauffeld's Leopard Frogs. I can call about 9/10 Leopard Frogs before looking at their femoral reticulums. There are some that I can be 100% confident on, and others that fall in that spectrum of overlap. But a 30 second "sum of its traits" minus the femoral reticulums, that I will discuss as we go through, usually points me in the right direction. That said, I am not going to make a distinct call on one of those "tougher" individuals until I see the femoral reticulums. This is truly one of those species in which, I feel, you need to hear or see the right features to be positive on the ID in most situations. When I say I can ID about 9/10 Leopards before getting them in hand, it is not to brag, but say that as someone that has worked with this species for years, there are still Leopards that I get wrong on occasion. If you want to listen to their calls, they can be found in each species respective profile.

Let's start discussing these three by first comparing range maps.

Pickerel Frog Range

Southern Leopard Frog Range

Kauffeld's Leopard Frog Range

Range should settle out a lot of questions. In all my experience, I have found no proof of Pickerels on the Eastern Shore. In nearly 25 years of living in Lunenburg and exploring Nottoway County intensely, I have never heard, seen, nor seen evidence of Southern Leopard Frogs in either county. There is some habitat that could favor Kauffeld's Leopards in far eastern Nottoway, but its pretty improbable they are really there either. We have found Kauffeld's in Cumberland as well as a few, oddly intermediate Leopard Frogs that we are just not sure about... Really, the lightest counties on the Kauffeld's map are just lit up because though I do not suspect them to be there, it is possible. If you are wondering why there is so much questioning, Kauffeld's Leopard Frog was described in 2014, and some sources claim it wasn't documented in Virginia until 2017. We really don't have a great collection of records as we do for other species due to the short time frame that we have considered this to be a species. We know more about this species from cryptozoology than herpetology at this point... Herping Virginia is is currently searching Amelia and Dinwiddie for more populations of this cryptic species.

Pickerel Frog calling from cover | © Ty Smith

Pickerel Frogs like ponds and marshes, while Southern leopards lake any grassy waterway (especially near pines) that isn't flowing too fast. Kauffeld's Leopards seem to favor Cypress and hardwood swamps, and are almost exclusively blackwater dwellers. We witnessed a spectacle one night in Greensville Co., where one side of the road was flooded cypress/hardwood forest, and the other was cutover with planted pines. We heard hundreds of Southern Leopards on the cutover side and dozens of Kauffeld's on the forested side chorusing all at once. I believe habitat is the key factor splitting these two into separate niches. This section of road boast both species while road cruising as well.

Pickerels and Southern Leopards though, will chorus in massive numbers. Dick Cross WMA has by far the largest numbers of Southern Leopard Frogs chorusing that I personally have heard at once, with a ton of Pickerel Frogs as well. The Spring Peepers there will deafen you as well, but that is getting off track.

Pickerel Frog vs Southern Leopard

Usually both frogs have a brown to olive base, but Southern Leopard Frogs often have a shade of green that sits on top of that base color. Pretty much, if there is bright green patches outside of spots on the dorsal, it is not a Pickerel Frog. Southern Leopards will usually have random darker spots down their dorsal. These spots are random in shape, and placement. Pickerel Frogs normally have large, similarly sized blotches (many describe as "squares") that run down the dorsal in two distinct columns (if you find the center of each spot and draw a line down them, they form a fairly straight line). I say "normally" as juveniles can be trickier, and I have seen some mutations that change the way the spots work, but I will cover that later. That said, it is fairly common these large spots link together and form one long, thick line. Sometimes you can see where one begins and another ends and they are clearly just touching, but some looks like chocolate melted and ran down the frog's back in a line. To me, on adults, these blotches are a night and day difference for these frogs. I can ID these adult frogs when we are road cruising from the car, through the windshield easily. This is not to brag or shame anyone who may struggle with these, but to point out the most likely reason people struggle with these is because we think of it as "one has a speck" and not as very distinct frogs.

Pickerel Frogs usually have full bands (or at least less broken ones) on their calves than Southern Leopards, which should only have broken bands. These bands usually contrast greatly on Pickerel Frogs compared to the Southern Leopard Frog. You might also notice a Pickerel Frog has a lot of bright yellow on its inner thighs. Pickerel Frogs are toxic, and this is likely to advertise their "distastefulness". I guess while taking about thighs, I should mention the femoral reticulums. These are patches of coloration on the thigh that hides under the folded calf. While it is not overly important in Pickerels, I figured I would point out the differences here.

Pickerel Frogs show bright yellows on their thighs | © Ty Smith

The figure above shows the high-yellow tones and larger blotches on the Pickerel Frog's femoral reticulum. I never use this to differentiate the two, mainly because I already have IDed any pickerel frog before I ever look at the usually hidden femoral reticulums, but if you are really struggling with one... Here it is...

One other key to IDing a Pickerel Frog, especially if it has a weird pattern, is the coastal fold. You may have to look at a few before getting a good feel for the species, but Pickerel Frogs have very thick coastal folds.

Juvenile Pickerel Frogs can be much looser with their pattern. I have seen them with randomly placed, and shaped spots. They can have pretty intermediate coastal folds as well. That said, the patterns on their calves should hep you determine what you are looking at. Pickerels should have those clear, bold bands even at this age, while Southern Leopards will usually have random spots unlike the normal calf spotting of the adults. This eventually corrects itself though. Juvenile Pickerel Frogs should have very yellow inner thighs as well.

I guess though I have kind of misspoke though, as I have focused this on Pickerel Frog vs Southern Leopard, but most of these apply to separating the Pickerel from the Kauffeld's Leopard Frog as well. All of this is pretty much for you to see the differences in the Pickerel Frog as to its two sister species. So, let's jump into the hotter subject; shall we?

Kauffeld's Leopard Frog vs Southern Leopard

Now, I hope you all have read my piece on average vs key traits, but if not I will give you the gist of it quickly. Average traits are traits that specimens of a species have most of the time (say 50% or more). For example, "Humans have brown or black hair.", is a good example of an average trait. The vast majority humans do have brown or black hair, but obviously not all. A key trait would be something that is the case nearly 100% of the time. For example, "Humans lack thick fur that covers the body." On average, Southern Leopard Frogs have a silver speck in the tympanum, and on average southeastern Kauffeld's Leopards do not. But as I mentioned this is only an average. If this is right 75% of the time (I am not sure the true number, but it is likely close), is that good enough for an average. I will try to be as clear as possible with these frogs, as there is a lot to cover. First off, I feel it is best to make two categories of Kauffeld's Leopard Frogs for Virginia: "Southeastern" and "Eastern Shore". You see, Eastern Shore Kauffeld's can be much more ornate, and tougher to distinguish from the Southern Leopard, than their Southern counterparts. I believe much of the, "You MUST have the femoral reticulums to ID." Comes from this population that only gets more and more Southern Leopard Frog like as you work your way up the Atlantic Coast into New Jersey and New York. I wouldn't dare wager a guess on the two that far north without looking at femoral reticulums, calls, or range maps, as the two become so similar, they exclude one another in these northern stretches. The Eastern Shore throws a mixed bag of obvious "one or the other", and "too close to call". So, what do we look for you ask? Well, let's cover the supposed dead-ringer first: femoral reticulums.

Southern Leopard Frogs will typically have tan to olive, or sometimes yellow, femoral reticulums with darker marbling across them. Kauffeld's Leopard Frogs have black femoral reticulums with white, yellow, or green patterns that look like stars in the night sky in my opinion. Sometimes these are not as clean as my figure above, but you have to pick where on the spectrum it falls.

Femoral reticulums are considered "the way" to ID these frogs, based on what we believe, I do not dispute this one bit. I feel it is quite important that we stay conservative when IDing these two species, as we just don't know enough about Kauffeld's Leopard yet. Truthfully, I have never seen a study into how effective femoral reticulums truly are for IDing these frogs with percents and exceptions. That said, if you are going to present a county record Kauffeld's Leopard Frog, you need these types of photos to vouch for you. One little "cheat" I have found is if enough of the waist is visible, you can see the same patterning on the waist and down a strip on the front of the thigh. This means, if you can see this, you should be able to make a call from that alone. That said, there are other differences, though they fit on a spectrum, and the spectrum slides the farther north you go. So, let's dive in a bit deeper so we can see these frogs as, and back-up our IDs with, more than just "markings on the thighs".

Kauffeld's Leopard Frogs are fairly muted in pattern. This a spectral trait, but a pretty good one in my experience. They just seem to have less spots, and these spots are more clean, especially on the flanks. Southern Leopard Frogs have many more spots on average. Below I have some Southeastern Kauffeld's Leopard Frogs and some Southern Leopards in the column next to them. This isn't about the colors, but compare the spot patterns on the dorsal and the flanks. I hope you can see how Kauffled's Leopards are lesser on the end of the spectrum when it comes to spot numbers than Southern Leopards are.

Dorsal and Flank Patterns

Kauffeld' Leopard Frog

Southern Leopard Frog

Now, are there exceptions, absolutely; and we will cover abnormalities later. But this is one factor we can use in the "sum of its traits" approach. I would probably not make an ID purely on this trait, but it is one more check box in the right direction.

One thing I believe can be as damning of a trait as any, is the snout. The Kauffeld's leopard is on the shorter, blunter snouted end of the spectrum, while Southern Leopard Frogs are on the longer, sharper, yet droopy end. There are some overlap in a few specimens, but once you learn this overlap, you will notice how obvious it is. This is another trait that once you get north of Maryland, things get trickier and more and more of these frogs teeter towards the center of this spectrum, but for southeastern Virginia and most of the Easter Shore, this is very helpful.

Southern Leopard Frog outside of Kauffeld's Leopard Frog range that has a pattern that looks very good for a Kauffeld's Leopard. That said, that snout is far too large for a Kauffeld's Leopard. | © Ty Smith

Funny enough, I have noticed that many Southern Leopard Frogs outside of the range of Kauffeld's Leopards look much more like Kauffeld's than those in the overlap. This probably helps the notion that those femoral reticulums are 100% necessary for an ID. Let's be honest here: it doesn't hurt to get photos of the reticulums. Science is often favored by the consensus, so without those reticulums most people are not going to be able to ID a Leopard Frog, and ones that will are going to be very seasoned and conservative herpetologist that know how the game is played and will say, "That looks very convincing for a Kauffeld's Leopard.", but really aren't going to flat out call it one or the other.

I personally think for iNaturalist purposes, if a frog has all the makings of a Kauffeld's, and is in known range and habitat, it should be good enough. If it looks like a Southern, than it is a Southern until proven otherwise. We can split hairs all day, but iNat is great for showing range and diversity. If it fits the bill for both, that is good enough for me. iNat ID's are suggestions, so why knit-pick them to death. That said, it is rare that I see a clear photo that I am confident enough in to call a Kauffeld's Leopard. Usually, if I call it a Kauffeld's Leopard, I would "bet my first born" that it is a Kauffeld's Leopard. Other wise I go to genus level. That's just my opinion on it all, as some people take stuff a lot more serious, and refuse to ID some animals that are similar even in range exclusions. Whatever floats your boat... It doesn't ever hurt to say, "I don't know."

Oddities

If you wonder why I think it is important to supplement the femoral reticulums with a "sum of its traits" approach, well it is because of random, oddball animals and basic diversity. So, I searched through iNat for some oddball frogs and I am going to explain why each one is what it is. These are not all necessarily VA specimens, but it doesn't mean VA specimens don't ever express these traits. And thank you to everyone below who kindly allowed me to use their photographs!

Pickerel Frogs

© Kimberly Fleming | Though this little guy has some crazy dorsal spotting, juvenile Pickerel Frogs don't always have linear spots. This is an extreme example of this. Note the bands on the calves are fairly complete, and the hint of yellow visible under the back leg.

© Alina Martin | This one is a particularly spotted Pickerel Frog. Note how thick the coastal folds are, and they yellow on the legs and waist. The thighs have some crazy, broken banding as well. My bet is that there is a rare gene that breaks the pattern into pieces, that is at play here.

Southern Leopard Frogs

© Ty Smith | This little guy was completely patternless on the dorsal! I see this rarely on Leopards, but I have never seen a patternless Pickerel Frog. In case you are wondering, Green Frogs lack the white fold seen on this individual that runs from the upper lip to the paired vocal sacs.

© Ty Smith | This guy was almost patternless with a only a few spots on the dorsal. He had yellow on the waist and vocal sacs, but it doesn't continue to under the leg and is not as deep as a Pickerel Frog.

© Ty Smith | What would you call this one? This photo was taken in North Carolina, outside of the KLF's range with dozens of other Southern Leopard Frogs. This is a Southern Leopard Frog, but would you have guessed correctly? How often can these femoral reticulums be wrong?

© Ty Smith | This is another wild-card specimen outside of the range for KLF. Specimen was calling, and femoral reticulums also favored Southern Leopard Frog, but the resemblances to a KLF is astonishing.

Still Unsure...

So... This guy above was found at a location that has both species. We heard him calling a very odd call, and I have to this day not heard another frog make this call. We snuck-up on him at the edge of a logging rut and caught him. My initial thought was Kauffeld's Leopard, but I noticed he had a intermediate nose. I looked at the thigh patches and it seems they were tan with dark mottling like a Southern Leopard, but with green patterns on top (similar to a Kauffeld's Leopard) of that as well. Some speculate it is a hybrid, while others a very weird Southern Leopard Frog. There is probably no way to actually tell without DNA analysis.

Closing

There you are. I hope that was helpful, though you may have less answers now than you have questions. That's fine! I do too. That is how science works. Even with femoral reticulums, I don't think we can ID every individual of the "Kauffeld's/Southern Leopard Frog Complex", and that is fine. Far more research needs to go into the range, habitat, diversity, and potential interbreeding of the KLF accross its range. All of this changes across a species' range, and much of it is not accounted for in literature of the KLF. Remember too that populations evolve as well. Though some things are black and white, there is a lot of gray looming in between.

That said, I hope it did make you more confident in Pickerel Frog ID. Oh, and I hope you squeeze Pantherana into every conversation that you can in the future; because, I will!