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About Author: Corinne Pisacane

Posts by Corinne Pisacane

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Catching Rock Iguanas: Easier Said than Done!

Corinne PisacaneThis year I traveled to the Turks and Caicos Islands to study wild rock iguanas. The Turks and Caicos rock iguana Cyclura carinata is endemic to this Caribbean country and is critically endangered. Our team flew to the island of Providenciales, the main hub for tourist travel. From there we continued in a much smaller plane across the beautiful and shallow waters of the Caicos Bank to our final destination, Big Ambergris Cay. This island, located about 40 miles east of Providenciales, is diminutive in size, measuring about 4 miles (6 kilometers) long and only 1 mile (1.6 kilometers) wide. Its highest point is less than 100 feet (30 meters) above sea level. In addition to the iguanas, this secluded island hosts a number of private residences, and there are plans for a large housing development, which poses a potential threat to iguana habitat on the island.

During my time on Big Ambergris Cay, I was involved with a graduate student’s dissertation project involving iguana capture, relocation, and the subsequent examination of homing abilities (among a number of other iguana-related activities!). Every day we set out after it warmed up enough for iguanas to come out of their nooks and holes. Once we located individuals of interest, we set about stalking them. A number of our team members then attempted to catch iguanas of interest with varying degrees of success. Sometimes the lizards were just too fast and would elude our attempts with ease!

Once caught, our next challenge was to try to take a blood sample from each iguana to measure baseline stress hormones. From the moment we caught each iguana, we had exactly three minutes to successfully collect the blood. Any time over three minutes meant that stress hormones (or glucocorticoids) had already reached the iguana’s circulation, meaning we were measuring its stress response to the capture, which was not our goal. As you can imagine, this made for a very exciting three minutes!

If we were not successful, the iguana would be released and not considered as part of the study. If we did succeed, the iguana was then numbered using a system of color-coded beads strung through Spectra line and placed on both sides of the iguana’s dorsal crest between the shoulder blades. This dorsal skin is similar to that of our earlobes, and the stringing of the beads is thought to feel much like piercing one’s ears. Once we were finished marking individuals with beads, each iguana was also fitted with a small radio transmitter to enable future tracking of their movements on the island.

After the identification beads and radio transmitter were secured, iguanas were released at their point of capture and tracked for two weeks to determine their home range. Then they were recaptured and relocated to a different study site just under a mile away to determine if relocation might be used to successfully mitigate future development. As soon as they were released, the race was on! Equipped with radio-receiver equipment, researchers tracked the movements of the iguanas daily to investigate where they went. It appears that adult iguanas can usually find their way home, although how they do so is still not fully understood. By contrast, the homing skills of juvenile iguanas don’t appear to be as developed, and they usually stay put in their new home. For this reason, juvenile iguanas make better candidates for relocation than adults.

Alongside all the capturing and relocating of iguanas, our team also processed all the blood samples collected. This was no small task, as the logistics of processing blood on a small Caribbean island are very involved and time sensitive. Samples had to be frozen immediately, which required transferring them from a portable mobile cooler, carried by each researcher, to a larger cooler on a golf cart (the only mode of transportation around the island!) and then, finally, back to one of our rooms where we’d set up a mobile laboratory. Overall, this was quite an operation! Picture at least half of a dorm room set up as a temporary lab with collection tubes, a centrifuge, slide-staining equipment, and blood-draw needles.

Having traveled to a number of tropical places, I had expected the Turks and Caicos landscape to be all soft sand and friendly flora, with iguanas living in a beach environment. How wrong I was! All this capturing, relocating, and tracking takes place on volcanic-like ground that can quickly tear up ordinary shoes. The ground is also uneven and makes capture and tracking a slow and strenuous process. In addition, the small shrubs and trees are full of thorns and are quite abrasive. As a result, we always wore long pants and covered up at all times, making the work more challenging as it got extremely hot outside. Thick-soled shoes were also critical if we were to move around quickly enough to capture iguanas and avoid large thorns entering the soles of our feet. While we find it difficult to deal with this kind of environment, the iguanas have evolved to be perfectly suited to it.

This type of research is critical to gain a thorough understanding of the biology and behavior of the Turks and Caicos rock iguana. As with most endangered species, we need to be diligent about setting aside the necessary habitat for these amazing reptiles. Rock iguanas throughout the Caribbean are in danger of losing their habitat as a result of human-related pressures. I learned a great deal while on Big Ambergris Cay and am very grateful that I could be involved with iguana conservation in such an amazing habitat!

Corinne Pisacane is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, ISWE: Cheetah Pseudopregnancy?

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Is Our Cheetah Pregnant?

CheetahThat’s the big question: did female cheetah Lindiwe successfully breed, and is she currently pregnant? Just last month we saw strong interest between Lindiwe and one of our proven breeder males, Noka. Lindiwe is a young cheetah, and this would make her a first-time mom, which is very exciting! From our point of view, the most important thing about getting a naïve female cheetah to breed is that once she breeds, she tends to continue having litters throughout her reproductive years. So the question remains: was Lindiwe actually in estrus and did not allow breeding, or did she simply not come into estrus during our breeding attempts? To answer the question, follow me into the Behavioral Biology Endocrinology Lab.

This lab offers us an opportunity to test hormone levels in a variety of exotic species. Hormone research adds an additional dimension to our research projects by providing another tool for unraveling the mysteries of animal behavior. When we are trying to test reproductive hormone levels in cheetahs, our preferred method involves non-invasive hormone sampling, a technique where the animals are unaware that we are testing their hormones. Blood collection can be a stressful procedure, which often results in adverse affects on reproductive hormones and/or behavior, so we usually sample urine, feces, and sometimes saliva and hair instead. The cheetahs go about their normal daily routine having no idea that we are testing their hormones levels!

Fecal (or poop) samples are collected by our cheetah care staff, promptly frozen, and brought to the lab for hormone testing. The first thing I do is dry the samples on a lyophilizer, a really big, fancy freeze drier that removes all the water from the fecal samples. I then crush and sift the dried fecal samples before weighing out a specific amount. I now have dried, weighed fecal material in a test tube and am ready to extract the hormones held within. There are many ways to do this, and they usually involve using a solvent in combination with some type of force. In our cheetah samples, I add solvent to the fecal material and mix (vortex) or heat the samples. At the end of this extraction process I am left with a test tube full of solvent that contains not only extracted hormones but also other extracted compounds. The trick is for me to find an appropriate laboratory procedure (or assay) that I can use to examine the concentrations of the specific hormones in question (in this case, female reproductive hormones). In humans, hormone assays are generally routine, but in exotic animals, extractions and assays can vary both between species and within species, depending on the hormones of interest and what biological sample they are from (fecal, urine, or saliva).

So back to the original question: was Lindiwe physiologically in estrus during the time she was showing the appropriate female sex behaviors? To answer this question, I needed to test her fecal samples for the hormone estradiol (a specific form of estrogen). In most species I could usually determine if the animal in question is cycling by looking at progesterone levels. But cheetahs are more complex as they are induced ovulators (see Cheetah Breeding Excitement). As such, their progesterone levels remain low unless a follicle, or egg, has actually been released from the ovary. To complicate matters further, when we study hormone levels in urine or feces, we usually only see metabolized hormones because we are looking at a waste product of the body. These are different from the hormones moving around in the bloodstream (known as parent or non-metabolized hormones) that are much easier to measure. Examining the concentrations of estradiol metabolites can be complicated and tricky because different animal species often metabolize hormones uniquely. These are the types of challenges we face in our endocrinology lab when studying hormones in exotic species.

After testing Lindiwe’s samples for hormones to see if she was truly in estrus during our breeding attempts, it appears that her rolling and tail flicking behaviors were somewhat misleading. Her hormone levels were quite low on the days she showed such estrus behavior. Interestingly, her hormone levels did go up, indicating a mild, short estrus, after we had stopped our breeding attempts. Welcome to the frustrating world of cheetah breeding!
We see a wide range of estrus behaviors varying from “silent” to “clear,” and some of our continual challenges include trying to decode the differences in behaviors between the females in our collection. We had very high hopes that Lindiwe was truly in estrus and would allow breeding by Noka, but alas, they did not end up breeding. We will continue our breeding attempts between the two, so please cross your fingers and hope for the best.

Corinne Pisacane is a senior research technician in the Behavioral Biology Division of the San Diego Zoo Institute for Conservation Research.

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Cheetah Breeding Excitement

I couldn’t wait to get to work this morning! My excitement surrounded yesterday’s developments at the cheetah breeding facility at the San Diego Zoo Safari Park. Our young, inexperienced female cheetah, Lindiwe, has been showing signs of estrus, and at long last our experienced male cheetah, Noka, has taken an interest in her. This is a very exciting development in the world of cheetah breeding!

I grab my raincoat and notebook and head over for more cheetah watching. Our breeding facility is not accessible to guests. After arriving, I try to control my excitement and optimism about the possible outcome of today’s breeding attempt. I’m pretty sure today is the day that Lindiwe and Noka will breed successfully.

My hopefulness increases as I view a short video recorded by our animal care staff just hours earlier, showing positive signs of interest between Lindiwe and Noka. These include both cheetahs laying down next to each other in their adjacent enclosures and touching noses through the fence. Noka then proceeds to make a vocalization called a stutter-bark in Lindiwe’s direction. The stutter-bark is a rarely heard vocalization primarily used by male cheetahs in breeding situations. We believe the stutter-bark plays a significant role in a male cheetah’s attempt to breed a female.

Listen to a cheetah stutter-bark:

[audio:http://www.sandiegozoo.org/animalbytes/sounds/cheetah_stutterbark.mp3]

To better understand the possible role of the stutter-bark vocalization, a little background on cheetah reproduction is needed. In most mammals (including humans), the release of eggs happens spontaneously and predictably (with cycles of varying length). However, there are a number of species that possess a different type of reproductive strategy where eggs are released from the ovaries after some sort of stimuli but not on a predictable cycle. The stimuli could include the physical act of mating, among many other possibilities.

In cheetahs, the stimuli that lead to egg release are not clearly understood. In the wild, female cheetahs are predominantly solitary, so we think that when a male encounters a female, the stutter-bark vocalization may be part of the reproductive strategy to help bring a female cheetah into estrus.

Our team moves Lindiwe to a neighboring enclosure while Noka is brought into Lindiwe’s enclosure, which he thoroughly investigates by patrolling the area, sniffing, and spraying. While he is investigating, we record details about both cheetahs’ behavior. We are hoping for a “strong” behavioral response from them, including both cats being very focused on each other, the female rolling on the ground and flicking her tail. Most of all, we are hoping that she won’t be aggressive toward him and that Noka will stutter-bark while pacing her fence line.

The breeding attempt continues for approximately 30 minutes, during which time we see the positive signs we are hoping for from both cheetahs. We decide to attempt an introduction between Noka and Lindiwe. At this point we’re also considering the possible downsides of an introduction with a female cheetah that may not be in estrus and, as a result, can be unpredictable and aggressive. This is definitely something we do not want in a breeding situation! Having weighed the costs and benefits, we move forward with our introduction: a keeper opens a fence separating Lindiwe and Noka while I continue observing and taking notes.

The breeding attempt begins positively, with no aggression from the male or female. Lindiwe is active and moving while the male stutters quietly toward her. He begins to follow her but occasionally gets a little too close, resulting in Lindiwe turning and moving toward him slightly. Then she turns and continues to walk around the enclosure. Noka is somewhat focused on her but is also not responding very strongly and appears to be somewhat distracted. After some time, we decide that the male’s response is not adequate and reluctantly separate the cats in the hope for a better response tomorrow.

If Lindiwe is truly coming into estrus, we expect to see a much stronger response from Noka. We do not currently have a scientific test that will tell us if Lindiwe is in estrus on the day of the introduction. If we attempt a blood draw, the possible stress associated with the procedure could affect the female’s reproductive hormones. Our current approach is to noninvasively examine Lindiwe’s reproductive hormones by collecting her fecal samples and determining her hormone levels back at the Behavioral Biology endocrinology lab. Stay tuned for my next blog post detailing the laboratory approaches I use to determine reproductive hormone levels in cheetahs and my determination (via hormone levels) of whether Lindiwe was truly in estrus during this breeding attempt.

Corinne Pisacane is a senior research technician in the Behavioral Biology Division of the San Diego Zoo Institute for Conservation Research.