The past month in Highlands County, Florida, has ushered in cool nights with fair weather days. The changing temperatures have signaled some changes in the behavior of the Eastern Indigo Snakes I am radio tracking as part of The Orianne Society’s study on the effects of habitat fragmentation and landscape change on Eastern Indigo population viability. After months of following these snakes through some of the harshest terrain south Florida has to offer, the snakes have finally started making it slightly easier for me to track them. Many of the Eastern Indigo Snakes we are studying seem to vary their seasonal habitat use from lowland hammocks, bayheads, creek banks, and grassy wetlands in the warmer months to the surrounding higher and drier scrub, sandhill, and flatwoods habitats in the cooler months. Part of this shift in habitat use is so that the snakes can have access to Gopher Tortoise burrows to use as refugia during cool winter nights, although Eastern Indigo Snakes in peninsular Florida can use a wide range of refugia, including stump holes, armadillo burrows, or debris piles, for winter shelter. This change in behavior and habitat use coincides with the start of Eastern Indigo breeding season which, strangely enough, actually occurs during the winter.
Breeding season for snakes in North America varies among species. Many species, such as Garter Snakes, Rat Snakes, Racers, and Water Snakes, breed during the spring shortly after emerging from their overwintering sites. Rattlesnakes typically breed during the late summer away from their overwintering sites, although some populations may have spring breeding as well. Eastern Indigo Snakes breed during the late fall and winter and male Eastern Indigo Snakes will move about searching for females during this time. This pattern of male mate-searching is also common in other snake species.
Male Eastern Indigo Snakes will also engage in male-male combat to fight for access to a female or defend her against other males. Again, this behavior is seen in other snake species, such as Eastern Diamondback Rattlesnakes. Some reports of Eastern Indigo Snake “mating” where two individuals are seen intertwined with the front halves of their bodies elevated off of the ground were actually two males engaged in combat. Although these combat bouts are usually just wrestling matches, males may bite each other and the combatants may depart with injuries. It is possible that smaller males may even be cannibalized by larger males, although this has never been proven in the wild. Like most snake species, Eastern Indigo Snakes, both males and females, probably mate with multiple individuals throughout the breeding season.
In the past two weeks I’ve had the great fortune of finding three new adult female Eastern Indigo Snakes that probably had something to do with our telemetered male snakes’ focus on finding females this year. I began noticing some unusual movements from one big male named Julius. Julius is an adventurer and regularly moves 1-2 kilometers in a single day. He has a favorite hiding spot beneath a pile of railroad ties that he probably uses for shedding or digesting a large meal. In the summer he would stay in this debris pile for about a week at a time before suddenly traveling to a lake edge about 1.5 kilometers away and staying there for a couple days before returning to his debris pile, presumably on a full stomach. This behavior continued until mid-October when he surprised me by going nearly the same distance but in the opposite direction towards some upland scrub and modified cattle pasture.
I tracked his location to a stump channel, recorded the usual GPS, weather, and habitat data, and began walking back towards the truck when a black sliver caught the corner of my eye. I dropped all my equipment and sprinted towards this new Eastern Indigo Snake as it quickly moved towards a large saw palmetto clump. I made a sliding catch, narrowly missing a prickly pear cactus, to grab her before she escaped. It was a female and would be very valuable for our telemetry research so the following day I drove her up to the UF Veterinary hospital in Gainesville for a transmitter implant surgery. The very next day I returned to locate Julius again and found his signal had moved again to the edge of a citrus grove and some scrub.
As I closed in on the signal, I saw him sitting atop a burrow entrance mound and then heard the unmistakable sound of another snake moving through leaf litter. However, I was looking right at Julius, sitting perfectly still, so my heart started racing again with the realization that he was probably courting another female! I turned my receiver back on to make sure that I was in fact looking at Julius so that I did not chase after the wrong snake and miss them both. I quickly got a visual of the new snake and made a diving lunge through scrub oak (once again narrowly missing an ominous cactus) to grab her before she made it into a nearby burrow. After the shock of catching two females in three days wore off, I decided to see how far Julius had moved off during the commotion. In fact, he had just crawled into the burrow he was formerly guarding and was now glaring out at me, understandably upset for stealing another female!
This week I was tracking another large male Eastern Indigo named Galileo when I glanced down to see yet another female Eastern Indigo Snake crawling across the road in front of me. After a brief chase through some tall grass I popped up with another gorgeous female Eastern Indigo Snake. This snake will also receive a radio transmitter and help us learn more about Eastern Indigo Snake ecology.
It appears that male Eastern Indigo Snakes in Highlands County are on the search for females and we have been able to capitalize on this behavior to add three new snakes to our study. The onset of cooler weather and Eastern Indigo Snake breeding season means that, on any given day, I just might find far more than I hoped for.