Tarantulas

Beginning in late June, the prevailing winds in the American Southwest change directions. Warm, moist tropical air from the Gulf of California suddenly finds itself being pulled into the dry Arizona landscape. With this influx of warm, moist air, the North American Monsoon begins. Storms pop up all over Arizona and the rest of the Southwest, but this rain doesn't come in the form of widespread and gentle storm fronts as it often does in Ohio. Instead, isolated, but intense, thunderstorms with torrential rainfall form around the region, dotting the landscape. On one typical July day during the summer field season, the dorms at the Appleton-Whittell Research Ranch in Southeast Arizona were surrounded by these monsoon thunderstorms.

The monsoon storms are a welcomed event for those living in the hot Sonoran Desert and semi-desert grasslands. Rain means a short respite from the soaring temperatures. But for a male tarantula, the rain means love is in the air. The monsoons signal the start of the mating season for the tarantulas in Arizona, and males begin an epic quest to find females. Males throw all caution to the wind and spend all the waking hours of the day wandering in search for a female tarantula's burrow. Since the females tend to stay in their burrow unless driven out by starvation or by a predator, it comes down to the males to seek them out. And that brings us to this male that we found hanging out on the dormitory at the Appleton-Whittell Research Ranch.

Meet the...uh... I'll be honest, I'm not sure what this species is.  Dr. Chris Hamilton, the author of the paper I discuss below, reached out to me and identified this as Aphonopelma chalcodes, the Desert Blonde Tarantula. The location (SE Arizona), habitat (semi-desert grassland), and golden carapace all help key this individual out to A. chalcodes. The Desert Blonde Tarantula is a tarantula in the genus Aphonopelma. Aphonopelma is one of the 100+ genera of spiders in the tarantula family (Theraphosida), and all of the native tarantulas in the United States belong to this genus. Although it is easy to get a tarantula in the western US down to genus, getting an individual down to the species level can be very difficult. In fact, no one is really sure how many species of Aphonopelma tarantulas are in the US, mainly because the Aphonopelma genus is (well, used to be) a complete taxonomic mess. But why though?

Okay, it’s time to delve into some science. What is a species? Although it seems like a simple question, it turns out it’s quite difficult to define what a “species” is, and it’s even more difficult to have the majority of biologists agree with a single definition. Most people have been taught that a species is a group of animals which can freely reproduce with each other. This is not really correct however, as many different species can hybridize with each other. The concept of a species is more complex than that. So then, what is a species? Well, there’s a lot of different concepts. In fact, there’s more than two dozen species concepts, and a list of the 26 most common ones throughout recent history can be seen here. Nowadays, most biologists define a species using the Unified Species Concept. This concept defines a species as a separately evolving metapopulation lineage. This definition isn’t as confusing as it may sound, and if you want to read all about it, please see Kevin de Queiroz’s 2007 paper at this link. I won't get into the details of the Unified Species Concept, but just know that our changing definition of a species has resulted in some problems when it comes to classifying animals.

Historically, animals were classified into species according to differences in morphological (or physical) characteristics. Aphonopelma tarantulas were one such group of animals. They proved quite a challenge though. As it turns out, many Aphonopelma tarantulas look very, very similar. Classification based on morphological characteristics became difficult, and the genus descended into a taxonomic chaos. Then everything changed when it became possible to look at the genetics of an organism. Being able to see how closely related or diverged one organism’s DNA is to another revolutionized the field of systematics (the field of classifying animals). With this new approach, scientists began classifying species based on their DNA. This approach uncovered an interesting secret. Scientists were finding that some animals which looked exactly the same (and therefore were thought to be the same species) actually had very different DNA. Thus the concept of a “cryptic species” arose. A cryptic species is one which looks exactly like another species, but in reality is a completely different one. A non-tarantula example of this would be the Northern and Southern Ravine Salamanders, which were previously thought to be a single species as they look exactly the same, but DNA analysis in 1999 revealed two separate species.

Of course, scientists decided to re-evaluate the Aphonopelma genus using a genetic approach. Maybe this would reveal some truth in the current taxonomic mess that was Aphonopelma. I want to stress that doing something such as revising an entire wide-ranging genus is a tremendous undertaking. First, genetic work is expensive. Second, you would need DNA samples from hundreds and hundreds of individuals in order to get a representative view of the evolutionary relationships, as tarantulas are so wide-ranging (they span throughout the south from the Mississippi River west to the Pacific Ocean). Getting enough samples is not only expensive due to the traveling necessary, but is also incredibly time intensive.

And this is exactly the undertaking that Chris Hamilton, Brent Hendrixson, and Jason Bond took on. This team of scientists from Auburn University and Millsaps College just published (Feb. 2016) a massive revision of the Aphonopelma genus. In this study, they combined the relatively new genetic methods of classification with the classical morphological and ecological methods in order to “delimit” the species within the genus. This integrative approach is much more effective and thorough than simply using any one technique alone. Before this study, there were 55 Aphonopelma tarantula species described in the US. This study found that there were actually only 29 true species. Only 15 of the 55 originally described species were supported by their findings. In addition, they described 14 new cryptic species. The rest of the originally described species were found to be either unsupported or a case of a single species getting named twice or more by separate scientists.

However, the authors pointed out that this is only the start. Although they sampled 1000+ tarantula individuals from a wide range of localities, there are probably many more species out there that they simply didn’t come across. Between incredibly remote and rough terrain, and the difficulty of finding individuals in the wild, it is probably nearly impossible to completely sample every species in the US. There are surely more species out there, but many of those are likely to be highly localized or in hard to access localities. If you want to learn more, I highly recommend reading the first several pages of this giant study (which comes in at a staggering 340 pages). The paper can be found at this link. 

 

I think it's safe to say that a lot of people probably fear tarantulas. They're big, they're fuzzy, and, gasp, they're spiders. Now, I love spiders, but I can understand the fear. Though, as with many animals, much of that fear is rooted in misunderstanding. Tarantulas in the United States aren't dangerous. None of the American species have dangerous venom. A bite from one is equivalent to a bee sting. It's not going to feel pleasant, but it's nothing to freak out about either. American tarantulas rarely bite though. A more common line of defense in the Aphonopelma tarantulas is their use of urticating hairs. These tarantulas have species bristles on their abdomen that, when the tarantula feels threatened, can be "thrown" off with their legs. The tarantula will throw these bristles toward the threat, where they will embed themselves in the skin. These bristles then cause irritation to a varying degree, depending on the species. This irritation is essentially just an uncomfortable burning sensation. It's similar to the kind of reaction you would get from touching Stinging Nettle. Even so, American tarantulas are pretty docile. It really takes some harassing for them to defend themselves, and that level of harassment should never even happen. If you leave a tarantula alone, they pose literally no threat to you at all.  

This is one of my favorite photos from the summer. I had set up a simple white backdrop in the lab for photoshoots with the lizards, and we decided to put the tarantula in it. He was a good sport for me and allowed a few shots before wandering off the backdrop and onto the table. I know not everyone will agree with me, but I think they're magnificent creatures. Finally seeing a tarantula in the wild has fulfilled a wish I've had since I was a very small child.

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This post ended up being a lot longer than what I had planned, but my intent on identifying this tarantula to species took me down the systematic rabbit hole. This post is a bit more science-heavy than usual, but hopefully I explained the concepts well! If you have any questions, or want a more in-depth explanation of something discussed, feel free to drop me a comment below! Thanks for reading! I would also like to thank Dr. Chris Hamilton for identifying this individual to species.

Bird Banding

Two weekends ago on the 15th I woke up as the sun was rising, donned four layers, and made the short trek to The Ridges in the brisk 16 degree weather. Why? To go bird banding, of course! One of the Ohio University graduate students specializing in ornithology has been setting up banding stations at The Ridges, and he invited the OU Wildlife Club to see what banding is all about. Sadly, the early time and the cold weather turned most people away. In the end, only me (the secretary), Alayna (the president), Olivia Brooks (who runs the Twitter account Wild Earth), and one other member showed up.

For those of you who've never been, The Ridges is a large tract of land now owned by Ohio University which sits on the outskirts of the city of Athens in Athens County. The main point of interest is the old "insane" asylum, but there's also dozens of acres of forests and grasslands with miles of hiking trails, which I've partially covered before. The graduate student set up a total of three nets near the Nature Walk Trail in order to catch and band birds. What exactly is bird banding though? Well, bird banding is where a certified bander will place a small metal ring on the leg of a wild bird that was caught in a "mist net." Each band has a unique number and that number, along with morphological data of the bird, goes into a giant database. The idea is to be able to mark an individual, recapture it at a later date, identify the individual, and then gather more data. On a large scale, this process helps us learn more about migration routes, morphology, age, and various other information.

So what did we catch that day? I'll start off with this Tufted Titmouse, Baeolophus bicolor. This common backyard species is a part of the tit and chickadee family know as Paridae. If any of you are birders, you're probably well-acquainted with these guys. Many of the species in Paridae are known to form medium-sized flocks during the winter; right about now you'll see flocks of chickadees moving throughout areas searching for food. The Tufted Titmouse is a bit different. They actually don't form winter flocks; instead a breeding pair will continue to stay on their summer territory and search for food. Many times one of the hatchlings from the previous summer might join them, as well as other random juveniles from the area. Occasionally they will join those chickadee-based flocks. These flocks have a very hierarchical nature, and the Tufted Titmice, when they're part of those mixed winter flocks, will assume the most-dominant role.

A closer look at the feet reveals extremely long, and very sharp, talons. Tufted Titmice are denizens of forests, particularly forests with dense canopies as these provide excellent cover and foraging opportunities. A large part of a Tufted Titmouse's diet is arthropods. These large, sharp talons help them grasp the bark of trees as they search it for insects, spiders, and the like. I'm always struck by just how dinosaur-like birds' legs are; it really makes sure you're reminded of their reptilian origins.

Also in the family Paridae is the well-known and much loved Caroline Chickadee, Poecile carolinensis. If you know nothing about birds, you have still probably heard about the chickadee. We have two chickadee species here in Ohio. Identification between these two species is difficult due to their very, very similar appearance, but typically this isn't a problem due to the fact most people are only in one of the species' range. If you're in Athens, for example, you know 99.9% of the chickadees you'll see are Carolinas. But Ohio, as I mentioned previously, has both species. Generally, to the north is the Black-Capped Chickadee, and to the south is the Carolina Chickadee. But this also means we have a dreaded transitional zone between the species. This roughly exists along the Lima-Mansfield-Canton line across the state. What makes this line even worse for birders, but cool for scientists, is the fact these two species will even hybridize within this zone.

 

Carolina Chickadees are very intelligent and interesting birds. Many times this species will act as "alarms" for other songbirds in the event of a threat coming into the area. Upon sighting a threat, Carolina Chickadees will many times give a buzzy "chick-a-dee-dee-dee" call, which is where they get their name. Interestingly, studies have found that the Carolina Chickadee tailors that chick-a-dee call to the severity of each threat. For example, one study (Soard, C., and G. Ritchison. 2009) found that for lower threats (such as a Red-Tailed Hawk, which would typically not hunt chickadees), Carolina Chickadees gave a call with more of the introductory "chick" notes than the buzzy "dee" notes. On the flip-side, predators posing a significant threat resulted in the chickadees giving a call with more of the "dee" notes than the introductory "chick" notes (if there were any "chick" notes at all.) If you're interested in that study, you can download a PDF from this link.

The largest bird we caught that day was this female Northern Cardinal, Cardinalis cardinalis. This bird, also called the "redbird" by some, is a very common species in Ohio. In fact, it's even the state bird (along with six other states). With most songbirds, only the male sings. Bird songs are employed by males to mark territories and to attract mates. With the Northern Cardinal, the females will also sing. While songs vary, both sexes will sing the same types of song.

The final bird we caught that morning was the ubiquitous Song Sparrow, Melospiza melodia. These are one of my favorite birds and they have one of my favorite songs. Song Sparrows don't actually have a "set" song; there's a whole range of bits and pieces that the Song Sparrow will string together to make one individual song. Many times a song will have certain parts which almost all use (like the 2 or 3 introductory notes which most songs start with), which allows birders to quickly know what they're hearing is a Song Sparrow, even though it might sound nearly completely different than any they've heard before. Song Sparrows will actually learn the songs of neighboring individuals and add them to their repertoire. An individual can know over a dozen different songs, many times with hundreds of small variations on those general songs. An individual can also improvise and tweak his songs and his learned songs to create new songs, which other neighboring individuals can learn and tweak themselves. As you can see, the Song Sparrow's use of songs is a highly complex endeavor. What's even more interesting is the effect they have on females. As I stated previously, males will use songs to attract females. Most of the times the females are attracted to the male's performance of a set species-wide song. With Song Sparrows, studies have found that females are also attracted to the male's ability to learn, which is reflected by the number of songs he knows on top of how well he actually performs them.

When the graduate student was taking measurements of the Song Sparrow, I noticed something a little odd. It looked like a tick was on the neck, and sure enough upon checking there was a blood-engorged tick attached to the neck. This tick is probably Ixodes brunneus, also called the Bird Tick. This is, as most ticks are, a bad thing. Not only do you have a blood sucking parasite, but these birds can contract a condition known as tick paralysis from these ticks. Many Ixodes tick species have a substance in their saliva which upon injection to a host will slowly paralyze that host. Eventually this can lead to death. We decided to remove the tick, so hopefully the sparrow will be fine.

That's it for this long post. It's currently Thanksgiving as I write this, and this has been the first time in a few weeks that I've had to sit down and actually write. Finals week is currently only two weeks away, so once again I'll be tossed into the college craziness when I head back to Athens this weekend. I've been slacking on posts recently and hopefully with break I can catch up. Thanks for reading!