Expanding at a Snail’s Pace

The Magee Limpkin feeding on a snail in the genus Pluerocera.

In early July 2019, a juvenile Limpkin turned up outside of Akron, Ohio, superseding the species’s most northerly US record from Maryland in June of 1971 by nearly 250 miles. News of the state record spread throughout the birding community, and by nightfall, a binocular-clad crowd had gathered around the suburban pond where the young bird was calmly feeding on snails. Reports soon flooded in that this was no isolated incident, either. Just a few days earlier, another bird had been seen in Mentor, Ohio. One month later, a third Limpkin was reported from Magee Marsh, and in mid-October, a fourth from Mentor’s Veteran Memorial Park.

Range Map of the Limpkin in North America (Source).

The Limpkin (Aramus guarauna) is the only member of its genus Aramus. Cross the long legs and serpentine neck of a heron with the skulking gait and plump body of a rail and you will have something that quite resembles a Limpkin. These brown and white birds are inhabitants of southern swamps from Florida to Central and South America where they specialize on apple snails (Pomacea sp.) and other freshwater mollusks. With such a specialized diet, it’s a small miracle that the Limpkin has survived the draining and dredging of its wetland habitat.  Limpkin population trends are poorly understood, but the species appears to be stable in Florida. Recent declines in the northern portion of its range may represent a contracting distribution, and historical records suggest the Limpkin once inhabited Mississippi, Texas, and much of Georgia. 

Sightings of Limpkins north of Florida and extreme southern Georgia are rare, but records of vagrant Limpkins reaching northern latitudes date back to 1950s when an injured bird was found in Nova Scotia, Canada. Sightings of Limpkins in northern latitudes are typically one-offs and are short-lived. The Magee Limpkin on the other hand, has been seen on and off for nearly five months. 

Ohio isn’t the only state in 2019 to see its first Limpkin record. In August, Illinois’ first confirmed Limpkin was spotted on a lake near the city of Olney. In 2017, Louisiana had its first Limpkin record when a group of four appeared in December. The following month, a pair successfully reproduced for the first time in the state. This represents breeding nearly 350 miles west of the nearest confirmed breeding record. Two years earlier, Georgia had its first state breeding record near Albany. Decade long surveys suggest that vagrant Limpkins have been turning up with increasing regularity since the early 2000s. Alabama, Georgia, and South Carolina have seen the bulk of these vagrants, but Limpkins have found their way to Maryland, Virginia, North Carolina, Tennessee, Mississippi, and now Louisiana, Illinois, and Ohio.  

A bird turning up outside of its natural range is nothing special. Major weather events like hurricanes can blow birds off course, landing them in states where they have rarely or never been recorded before. In 2013, a Brown Pelican, a native of the Atlantic, Pacific, and Gulf coasts, awed birders when it spent the summer along Lake Erie after being swept up by a low pressure system. It represents only the third record of a Brown Pelican in the entire state.

For recently fledged birds, migration has a steep learning curve. Juvenile Scissor-tailed Flycatchers follow their parents as they use visual, magnetic, and celestial cues to navigate. These internal compasses allow them to travel from the prairies of central North America to the southern Caribbean and back each year. During these travels, juveniles can often become disoriented, landing them well outside the usual range for their species. Migration is not all learned either. Sometimes, a genetic mutation can cause a bird's internal navigation system to go haywire. This may partially explain why scissor-tailed flycatchers (as well as many migratory species) occasionally deviate from their set migratory trajectory and have been sighted across North America from Alaska to Nova Scotia. 

Then there are the dispersers, which Joseph Grinnell described as “the exceptional individuals that go farthest away from the metropolis of the species; they do not belong to the ordinary mob that surges against the barrier, but are among those individuals that cross through or over the barrier.” Dispersers travel farther than 90% of the population and are responsible for the rapid colonization of human-introduced species like the European Starling and House Finch. How else would birds that rarely travel farther than 50 km in a lifetime colonize eastern North America from one, small founding population in just a few decades? 

Due to its exploratory nature, dispersal is a highly risky endeavor, and many birds do not survive their forays into unknown territory. In 2018, a juvenile Great Black Hawk, a species native to central and South America, was found in Maine. It represents the first and only record of a Great Black Hawk in the US. Just why this bird traveled from the tropics to the northern forests is a mystery. The hawk was able to sustain itself on a diet of gray squirrels throughout the summer, but as winter encroached, the tropically-adapted bird suffered severe frostbite and later died in a rehabilitation center.  

When successful, dispersal acts as a positive feedback loop for population growth. Lucrative years of reproduction increase the odds some juveniles will be genetically predisposed to wander. Establishment of new populations by a few lucky dispersers bypasses the slow expanse of home range leapfrog that most individuals employ to avoid inbreeding. Newly colonized habitats are not subject to the same limiting resources that stall population growth, allowing a rapid expansion of the species across a wide geographic area. 

So what is responsible for Ohio’s sudden Limpkin mini-invasion? Limpkins are non-migratory birds, and the first sighting in early July and August precede the hurricane season. Following sightings have not been linked with any major storm events. A single Limpkin might indicate a faulty navigation system, but mutations are rare events and are unlikely to account for the multiple Limpkin arrivals in northern states. Juvenile birds dispersing from their natal territories seem the most likely explanation.  

Range of the native Florida Apple Snail (Pomacea paludosa). (Howells 2006).

Limpkins are closely tied to the distribution of their primary prey, the Florida Apple Snail (Pomacea paludosa). Florida Apple Snails are the only native apple snail in the continental United States and make up over 70% of the Limpkin’s diet. Extending from peninsular Florida to the panhandle to the southern edge of Georgia, the Florida Apple Snail matches the distribution of the Limpkin almost perfectly. Extensive wetland loss during the 20th century greatly reduced the density of native apple snails and contributed to Limpkin population declines and local extinctions. Today, the Florida Apple Snail is considered an indicator species for successful wetland restoration. 

A large invasive Island Apple Snail from Arthur R. Marshall Loxahatchee National Wildlife Refuge in Florida.

In the late 70s, several species of non-native apple snail, including the Island Apple Snail (Pomacea maculata), became established in the US. Due to this snail’s greater size and fecundity, it has been able to outcompete the native Florida Apple Snail and has spread from North Carolina to Texas and across much of the southeastern US. 

Range of introduced Island Apple Snail (Pomacea maculata formerly P. insularum). (Byers 2013).

Invasive apple snails are veracious consumers of aquatic vegetation and pose a serious threat to agriculture and native ecosystems. As they consume algae, these snails bioaccumulate toxins that make them a health hazard to both humans and wildlife. Snail neurotoxins have been linked to Avian Vacuolar Myelinopathy (AVM), a lethal neurologic disease found in waterbirds and raptors. Snails can also carry rat lungworm (Angiostrongylus cantonensis), a parasite that causes eosinophilic meningitis in humans.

The invasive P. maculata is a tropical species, and while it is currently limited to a handfull of southern states, climate change is poised to expedite its invasion. On average, ten new P. maculata populations are discovered each year. Many biologists feared that the replacement of the native Florida Apple Snail with its larger, tropical relative would spell doom for apple snail specialists like the Limpkin and the endangered Florida Snail Kite (Rostrhamus sociabilis). These larger snails are harder for juvenile Snail Kites to handle, reducing their ability to forage and, in extreme cases, leading to starvation.

Snail Kite from Loxahatchee. 

What is truly remarkable, however, is that these hardy invasive snails seem to be supplementing the declining native P. paludosa and have jump started Limpkin and Snail Kite population growth. Both species have been documented readily feeding on invasive snails, and the latter may even be adapting to this novel prey (Snail Kites are increasing in body size and bill length). The introduction of P. maculata into novel watersheds has been directly linked with Limpkin range expansion. Limpkins were once exceedingly rare in Lake Seminole, Georgia, but following an unprecedented increase in P. maculata, some twenty birds were recorded in 2017. The first Limpkins to breed in Georgia did so within 5 km of the first P. maculata colony to become established in the state. Nearly all vagrant Limpkins in Georgia, South Carolina, and Alabama have turned up in watersheds that have known populations of invasive apple snails. 

So there we have it; a growing population in the stronghold of their range has allowed Limpkins to disperse into new regions of the country. Even the small, imperiled population of Snail Kites seems to be following this trend. In October, the first record of a juvenile Snail Kite was reported from Presque Isle, Pennsylvania. But will these birds survive in the northern latitudes? Ohio has no native or invasive apple snails. While we do have our own introduced species of large snail, the Chinese Mystery Snail (Bellamya chinensis), our winters can drop well below freezing for months on end. Establishment of a new Limpkin population in the northern US is extremely unlikely. The best we can hope for at the moment is that our vagrant birds will leave for the winter, and if Limpkin populations continue to grow and expand in the southern US, Limpkins may become increasingly common Ohio vagrants.

Limpkin from Loxahatchee feeding on a mollusk. 

References

Bloom, P. H., Scott, J. M., Papp, J. M., Thomas, S. E., & Kidd, J. W. (2011). Vagrant western Red-shouldered Hawks: origins, natal dispersal patterns, and survival. The Condor, 113(3), 538-546.

Byers, J. E., McDowell, W. G., Dodd, S. R., Haynie, R. S., Pintor, L. M., & Wilde, S. B. (2013). Climate and pH predict the potential range of the invasive apple snail (Pomacea insularum) in the southeastern United States. PLoS One, 8(2), e56812.

Cattau, C. E., Fletcher Jr, R. J., Kimball, R. T., Miller, C. W., & Kitchens, W. M. (2018). Rapid morphological change of a top predator with the invasion of a novel prey. Nature Ecology & Evolution, 2(1), 108–115. https://doi.org/10.1038/s41559-017-0378-1

Cattau, C. E., Martin, J., & Kitchens, W. M. (2010). Effects of an exotic prey species on a native specialist: Example of the snail kite. Biological Conservation, 143(2), 513–520. https://doi.org/10.1016/j.biocon.2009.11.022

Chaine, N. M., Allen, C. R., Fricke, K. A., Haak, D. M., Hellman, M. L., Kill, R. A., ... & Uden, D. R. (2012). Population estimate of Chinese mystery snail (Bellamya chinensis) in a Nebraska reservoir.

Cottam, C. (1936). Food of the limpkin. The Wilson Bulletin, 48(1), 11-13.

Dobbs, R. C., Carter, J., & Schulz, J. L. (2019). Limpkin, Aramus guarauna (L., 1766)(Gruiformes, Aramidae), extralimital breeding in Louisiana is associated with availability of the invasive Giant Apple Snail, Pomacea maculata Perry, 1810 (Caenogastropoda, Ampullariidae). Check List, 15, 497.

Greenwood, P. J., & Harvey, P. H. (1982). The natal and breeding dispersal of birds. Annual review of ecology and systematics, 13(1), 1-21.

Horgan, F. G., Stuart, A. M., & Kudavidanage, E. P. (2014). Impact of invasive apple snails on the functioning and services of natural and managed wetlands. Acta Oecologica, 54, 90-100.

Howells, R. G., Burlakova, L. E., Karatayev, A. Y., Marfurt, R. K., & Burks, R. L. (2006). Native and introduced Ampullariidae in North America: History, status, and ecology. Global advances in the ecology and management of golden apple snails, 73-112.

Kennedy, T. L. (2009). Current Population Trends of the Limpkin (Aramus guarauna) in Florida. Florida Scientist, 72(2), 134.

Marzolf, N., Smith, C., & Golladay, S. (2019). Limpkin (Aramus guarauna) establishment following recent increase in nonnative prey availability in Lake Seminole, Georgia. The Wilson Journal of Ornithology, 131(1), 179-184.

Mills, E. L., & Laviolette, L. (2011). The Birds of Brier Island, Nova Scotia. Nova Scotian Institute of Science.

Mouritsen, H. (2001). Navigation in birds and other animals. Image and Vision Computing, 19(11), 713-731.

Posch, H., Garr, A. L., & Reynolds, E. (2013). The presence of an exotic snail, Pomacea maculata, inhibits growth of juvenile Florida apple snails, Pomacea paludosa. Journal of Molluscan Studies, 79(4), 383-385.

Rawlings, T. A., Hayes, K. A., Cowie, R. H., & Collins, T. M. (2007). The identity, distribution, and impacts of non-native apple snails in the continental United States. BMC Evolutionary Biology, 7(1), 97.

Ricciardi, A. (2015). Ecology of invasive alien invertebrates. In Thorp and Covich's Freshwater Invertebrates (pp. 83-91). Academic Press.

Smith, C., Golladay, S., Waters, M., & Clayton, B. OF LIMPKINS AND APPLE SNAILS: INVASIVE SPECIES, NOVEL ECOSYSTEMS, AND AN UNCERTAIN FUTURE.

Veit, R. R. (2000). Vagrants as the expanding fringe of a growing population. The Auk, 117(1), 242-246.

Wilcox, R. C., & Fletcher Jr, R. J. (2016). Experimental test of preferences for an invasive prey by an endangered predator: implications for conservation. PloS one, 11(11), e0165427.

A Field Guide to the Birds and Birders of Magee

Black-throated Blue Warbler (Setophaga caerulescens)

In early spring, weather radars pick up dozens of mysterious “little blue donuts,” moving across north America.  These bizarre weather patterns aren't weather at all.  They are hundreds of thousands of migrating birds traveling in mass nocturnal flocks to their northern breeding grounds. 

Radar image of migrating birds.

The most famous Ohio migrants are the neotropical warblers.  Many of these small, insectivorous songbirds nest in the northern latitudes during the spring and summer.  Once fall sets in, their insect prey begins to die off and the birds head to Central and South America where food is abundant year round.  As photoperiod (day length) increases in spring, the warblers’ internal clocks tell them it’s time to move north.  There is less competition in the northern breeding grounds than in the tropics, and an abundance of untapped resources as insects begin to emerge.  This makes for ideal nesting habitat—the only trouble is, the breeding grounds and wintering grounds are thousands of miles apart.

Magnolia Warbler (Setophaga magnolia)

Some species, like the Prothonotary Warbler, can travel some 5,000 miles in just three weeks. Warblers heading to Canada must cross Lake Erie in the process.  Before embarking on this arduous, long-distance flight, entire flocks drop down to the lakeshore to refuel, turning the forested wetlands along the Lake Erie Peninsula into a "Migrant Trap."  During the first weeks of May, Magee Marsh, Ottawa National Wildlife Refuge, Howard Marsh, and Maumee Bay become some of the best locations in the state (and the country) to see a plethora of species in a very small area.  In their pre-migration gluttony, the birds display little fear of people.  They can get so close that telephoto lenses are often completely useless.

Prothonotary Warbler (Protonotaria citrea)

Magee Marsh is Disney World for Wildlife Watchers.  It’s famous.  It’s crowded.  But, depending on who you ask, it just might be worth the hype.  I have visited the Magee boardwalk many times over the past few years, but never during the famed “Biggest Week in American Birding.”  I’ve always been a little too early or a little too late for the mass arrival of over twenty warbler species.  Each trip still brings loads of birds, unusual rarities, and a lifer or two, but I’ve always been curious about the Big Week.  On May 10th of this year, I headed up to Birder Mecca, braving the crowds for the promise of rare migrants.

Cape May Warbler (Setophaga tigrina)

Magee is as much about the birds as it is about the bird watchers themselves.  This is ground zero for everyones’ binocular-clad grandparents and eccentric, RV-driving uncles.  Spend just five minutes at Magee and you’ll invariably encounter dozens of these indigenous boardwalk rarities.  Around the wooden path’s main entrance you might have to bob and weave between several mated pairs of Beige-legged Tickers, spectacled older-couples leafing through their field guides murmuring to one another about the “white eye-ring” they just saw as their partner jots down another species to the list.

Northern Parula (Setophaga americana)

A little bit further on and you’ll start encountering Three-legged Sit and Shoots.  These old-fogies gather in prime ambush locations, having lugged their enormous cameras on flimsy monopods through the crowd.  Any bird that startles them by jumping into the open will be met with a defensive clatter of snapping shutters to scare it back into the brush.  If the bird is particularly persistent, you can expect a Flashing Pacer to arrive and finish the job with a few shots from a mounted speed light.

Chestnut-sided Warbler (Setophaga pensylvanica)

Flocks of Bobbing Looker-ons whisper amongst one another, chattering to any unlucky newcomer about the bird that was last seen ten minutes ago.  The real rarities are usually located by the flock’s Sharp Spotters.  These energetic, audible field guides migrated to Magee years ago and never really left.  They have seen it all (or so they say) and are all too happy to lead fledgling Looker-ons to new lifers, for a small fee.

Bay-breasted Warbler (Setophaga castanea)

I kid of course.  While there are a few birding practices I really do find distasteful (like those Flashing Pacers with their lights), I think it is inspiring and a bit humbling to see so many people captivated by this yearly, natural spectacle.  Magee is a place to meet fellow wildlife enthusiasts and reconnect with old friends.  In all my time pursuing wildlife, I’ve never experienced anything quite like it.

Tennessee Warbler (Leiothlypis peregrina)

On sunny mid-morning days during the Big Week, birds might be outnumbered ten to one by birders, but don't let that fool you about the shear abundance and variety that can be found here.  Like fish that occupy different water columns in an aquarium, there is a bird for every level of the swampy woodland.

Palm Warbler (Setophaga palmarum)

Keep a close eye on the ground for little, brown birds with bobbing tails.  The Northern Waterthrush can be expected anywhere the ground is wet.  Despite its name and drab colors, this is in fact a warbler.  Another thrush-like ground-dweller, the Ovenbird, is a common species throughout much of the state.  Moving up into the understory shrubbery, you can expect to see foraging Black-throated Blue Warblers, Palm Warblers, and the occasional Wilson's Warbler.  Be sure to take a second look at any peculiarly patterned nuthatches—they might turn out to be Black-and-White Warblers creeping up the tree bark.  

Northern Parula (Setophaga americana)

At the mid-level range, a good day will bring Magnolia warblers, Cape-may warblers, Bay-breasted warblers, Black-throated Green Warblers, American Redstarts, and Prothonotary Warblers.  Two of the most common warbler species often dominate this section of the forest: Yellow warblers and Yellow-rumped Warblers.  The dense, shaded vegetation may harbor Hooded Warblers, or the rare Canada Warbler.  

Black-throated Green Warbler (Setophaga virens)

You might have to strain your neck peering into the canopy to spot these warblers, but with any luck it'll be well worth it.  Foraging in the very tops of the trees are Northern Parulas, Tennessee Warblers, Nashville Warblers, and maybe even Cerulean Warblers.  My favorite of the bunch, the Blackburnian Warbler can be seen picking insects off the ends of branches right above the boardwalk.  

Extreme rarities occasionally turn up at Magee during the Big Week.  Saying the words Connecticut warbler, Mourning Warbler, or the endangered Kirtland’s Warbler on the Magee boardwalk is akin shouting fire in a crowded theater. 

Blackburnian Warbler (Setophaga fusca)

If you are just getting in to birding, then the shear number of similar-looking warbler species might be a bit daunting (it certainly was for me).  In that case, I’d recommend a spring trip to Magee even more.  There is no better way to learn your birds than getting out in the woods with a pair of binoculars.

And, if all else fails, just ask the birder next to you what he or she is looking at. 

Yellow Warbler (Setophaga petechia)

More soon!

Keep living the field life

Ryan

Tale of Two Salamanders

I held tight to my camera as the truck lurched forward, front tires plunging into several inches of mucky water.  Carl and I had chuckled at the prominent yellow signs, declaring “road may flood,” on the way in.  With each pass around the forested wetland, the water had risen by several inches, sinking our tires further and further into the oily blackness.  With the road now well under a foot of water, I was beginning to question our bravado.  “What is that!?” Carl exclaimed as something furry and brown half scurried, half swam out from under our advancing vehicle.  It was a muskrat, swimming over the two lanes like this was just another stream.  As the aquatic rodent dove under the surface, its body undulated, revealing a long, flattened rat-like tail.  

Getting stuck on some back country road an hour south of Athens wasn't on my to-do list for the night. Thankfully, Carl's trusty four-wheel drive pickup rumbled heartily through the deepest stretches of water. I hadn't anticipated how quickly the surrounding wetlands would overflow, turning the entire landscape into one big vernal pool.  As the rains picked up, the light traffic dropped to about zero.  This was good for migrating amphibians and other water-logged wildlife, but I wondered how long it would be before anyone noticed us if we did get stranded out here.

Cambarus bartonii cavatus an undescribed species.  Note the dozens of babies under its tail.

Reaching higher ground, we spotted something small and shiny crawling lamely over the asphalt.  Expecting an injured amphibian, I was instead met with the largest crayfish I had ever seen.  This land-dwelling crustacean (Cambarus bartonii cavatus, evidently an undescribed species) was a good sign for the mole salamanders we were looking for.  Crayfish dig extensive burrows in the surrounding woodlands, lawns, and agricultural fields, providing fossorial amphibians with a refuge during the summer and winter months.  Rain floods these burrows and forces their occupants to find new hiding places.  Whether it be invertebrates, amphibians, reptiles, or even mammals, rain makes wildlife move.  As we drove along, the eyeshine of an opossum was illuminated by our headlights; the two eery points of green light faded back into the darkness as the gray, shaggy marsupial moved away.

Spring peepers and wood frogs hopped across the road every few feet.  Their high pitched whistles and guttural whines resonated from the nearby pools and streams.  Carl hadn't visited these routes for a few years (save for a brief trip we made in late autumn).  I was impressed that he retained a mental map of the area.  When I road cruise (the term herpers use for driving around and looking for amphibians and reptiles), I usually creep along at 15-20 miles per hour.  Any faster and I worry I’ll miss or hit something.  Carl, on the other hand, does something more like speed cruising.  Rocketing down the backroads, he straddles anything that could be alive, then rapidly backs up for a better look.  It’s efficient and effective, but for someone like myself who can get motion-sickness sitting in a parked car, it’s a bit of a challenge.  I tried to focus on scanning the pavement for movement as we zipped along.  It was a good distraction, but no replacement for getting out into the fresh air.  

The streamside salamander (Ambystoma barbouri)

After a few stops to inspect peepers, wood frogs, and spotted salamanders, there, stretched across the pavement—a salamander I had never seen before.  Upon closer inspection, nothing was particularly striking about this unassuming salamander.  Its body was chunky, though smaller proportioned than a spotted or a jefferson.  It displayed no bright colors or distinct markings; two shades of light gray frosted its back and sides.  The head was held high, peering up at us—an unusual behavior for this stubborn species.  Its head was also disproportionately small and snub-nosed, at least for a member of the “logger-headed” mole salamanders.  A thin, yellow line stretched across its rounded face—giving the salamander a content smile.  

“That’s our barbouri,” Carl commented as he looked down at our find.  Ambystoma barbouri, the streamside salamander.  Streamsides are unique among mole salamanders—not for their appearance, but for their behavior.  They don't breed in the temporary vernal pools that other members of this group migrate to every spring or fall.  Instead, their courtship and egg laying takes place in shallow headwater streams.  They attach their eggs to the underside of flat stones, and after hatching, the larvae grow and develop in these streams.  A. Bourbori occupy a limited range in southwestern Ohio and other nearby states where they inhabit upland forested hillsides during the summer.  

Travel just a few counties north of the streamside’s range, and you might encounter a salamander that looks nearly identical.  Until as recently as 1989, the streamside salamander was thought to be a stream-dwelling form of Ambystoma texanum, or the small-mouthed salamander.  Small-mouthed salamanders differ in appearance from the streamside in a few unremarkable ways.  They have a slightly longer snout, unique dentition with two rows of teeth, and a more wedge-shaped tail.  The most important behavioral difference is that small-moutheds breed in vernal pool habitat like the rest of the mole salamanders.  It is thought that about 4 million years ago, these two species split when A. barbouri began utilizing stream habitats.  However, breeding behavior is not a sure-fire way to tell these species apart, as both texanum and barbouri have been reported utilizing both streams and pools.

The following night, Carl and I traveled an hour north of Athens.  On a short stretch of road that cut through a patch of forest between a cornfield and tiny town, Carl spotted a single small-mouthed salamander.  Another lifer for me.  Small-moutheds inhabit lowland forests, floodplains, and fields.  If I hadn't known differently, I never would have made the distinction between this individual and the salamander from the night before. 

The small-mouthed salamander (Ambystoma Texanum)

This classic case of a cryptic species is made even more confusing by the genetic netherworld that these salamanders emerge from.  The more widespread and abundant Small-mouthed salamander (found from Ohio to Texas) is commonly parasitized by the ambystoma unisexual complex.  This group of all-female salamanders actually steals genetic information from other salamander species and incorporates it into their polyploid (more than two sets of chromosomes) genome.  This can result in animals that look quite like small-mouthed salamanders but who don't belong to the species and who might also contain the genetic information of blue-spotted salamanders and even tiger salamanders.  

In areas where A. texanum and A. barbouri overlap, some interbreeding, either historically or on going, is thought to occur.  This can blur the line between these two species and endanger the unique genetic identities of each (particularly A. barbouri due to its much smaller population).  To determine range maps where different species live, genetic testing is often helpful when dealing with cryptic species.  

When it comes to barbouri and texanum, however, genetics is another hurdle herpetologists must overcome.  The interbreeding that has taken place between these two species has left its signature in the genes of some A. texanum.  This phenomenon is called mtDNA introgression.  Mitochondrial (mt) DNA is inherited from the mother, and doesn't change much from generation to generation.  This makes it important for determining unique species lineages.  What's so difficult for this species in particular, is that entire populations of small-mouthed salamanders possess the mtDNA of streamside salamanders left over from interbreeding events.  Individuals with this condition can still be told apart by their anatomy, but this often requires collection or dissection, something most herpers aren't prepared or willing to do.  

The small-mouthed salamander we found on the second night was from a population that possess the mtDNA of the streamside salamander.  While this lends some question as to the true identity of these salamanders, the population is continuous with the known small-mouthed range.  For this reason, as well as anatomical features, we are comfortable calling them true small-moutheds.  This really shouldn't be the stopping point, however. Countless more questions need to be asked in order to expand our knowledge and better our understanding of these unique and unusual creatures. 

Even when they seem dull or indistinguishable, herps often hide some baffling secrets.  Salamanders are funny that way.  These slimy puzzles force us to think outside of what's familiar and comfortable.  I think that's why they fascinate me so much.