By Laurel Serieys, PhD
As a biologist leading the Urban Caracal Project, the project has offered me a number of stand-out rewarding moments– and quite a number of fortuitous surprises too. The story of Tyger is just one of those...
Tyger is a young male caracal, probably close to 2 years old, that was the 18h caracal for the Urban Caracal Project, and the 16th that we radio-collared. He's quite an interesting cat! He was hit by a car in the northern suburbs of Cape Town late last year. One of his legs was broken, but it seemed that if the leg could heal, he would survive. The Cape of Good Hope SPCA worked to rehabilitated him. He had surgery to fix the broken leg and was carefully monitored and cared for.
Within a couple months time Tyger was ready to be released. With the help of a SANParks colleague and permission granted by the SPCA, on December 23, 2015, we radio-collared Tyger. He was then released into the Tygerberg Reserve near the suburbs where he was initially found hit by a car. I personally expected Tyger to remain in, or nearby, the reserve until his radio-collar ran out of battery power.
Because of this prediction, I'd been worried that using our limited resources to collect data on him could be a gamble...would I trust the data? Here would be a caracal that had a broken leg that was repaired in captivity– a very stressful environment for a wild animal. If Tyger just hung around the reserve, would that be because his leg wasn't completely healed, or would it reflect his natural behavior? I felt I wouldn't ever know for sure, but I did happen to have a radio-collar that had only half-battery after it was recovered from the body of another caracal, Berg Wind, that died of disease. So if the data were questionable, I didn't feel this use of Berg's half-battery collar would be too big a loss.
But what a surprise Tyger has proven to be! After only 10 days of laying low in the urban reserve (map above), Tyger was ready to take off!
Tyger found a narrow strip of relatively connected habitat and used the corridor to leave the reserve (map above).
And then straight north he went all the way to Malmesbury! He made a 55 kilometer trek, suggesting that he was in dispersal mode, looking for an unoccupied territory to call his own.
Dispersal behavior of young males and Tyger as a case-study
Despite all the challenges Tyger was up against, he turned out to be just the case study I was looking for. When young male wild cats reach approximately 2 years in age, they "disperse" (move away from the area where they were born), sometimes even hundreds of kilometers, depending on the species. This behavior is a natural deterrent to inbreeding in populations. The females of most species tend to stay closer to where they were born, so if the males move long distances, both emigrating out of and immigrating into populations, genetic variation in populations can be maintained and inbreeding avoided.
In the Cape Peninsula, where the majority of our caracals are radio-collared, we presume the area is absolutely isolated by urbanization. So far, we have not seen any individuals leave the Peninsula. And so, in this landscape isolated by a sea of water and dense urban development, how is effective dispersal to occur so that inbreeding is avoided? Fortuitously, at around the same time that Tyger made his long-distance trek, another young male that we radio-collared within the Cape Peninsula exhibited similar behavior. But the distance from south to north for the entirety of Table Mountain National Park is roughly 50 kilometers. Azure, caracal # 16, showed us there's not much of anywhere to go. We recently highlighted these observations on one of our Facebook infographics.
So what happened to Tyger and Azure after their journeys?
Tyger's story could be one of success. He seems to have settled down in the Malmesbury area where there are agricultural and reserve open spaces that likely provide great hunting ground for him. It is unfortunate that his collar ran out of battery before we established how he would settle in, but the last of his movements spanning approximately 6 weeks suggest he was exploring a potential territory of his own.
Where Tyger is settling is very near to West Coast National Park, and while we watched Tyger's movements with bated breath wondering if he would journey all the way to the National Park, he doesn't need to go that far. These cats are resilient and adaptable do remarkably well even in landscapes fragmented by agriculture and urbanization.
Azure's fate, on the other hand, is less certain. During his dispersal effort, he moved as far north as he could- all the way to Signal Hill. He ping-ponged around Signal Hill for about a week before turning around and heading back towards where he started– Silvermine/Tokai area. Given that he was caught in that area, I was wondering if he would next go south to explore potential territories in South Peninsula. But he hasn't. He continues to hang around Tokai, occasionally heading towards Constantia, but his options are limited. Unfortunately, his collar will soon run out of battery, but the data we've collected from him has been fascinating and teaches us a lot about frustrated dispersal efforts for Cape Peninsula caracals.
So what can we do with this knowledge?
At many of the talks I've given, a lot of people will raise the point that if caracals in the Cape Peninsula are absolutely isolated- they must be doomed and what's the point of trying to protect them? I often point out that it is important to think both smaller and bigger picture. First, caracals are showing us that they are extremely resilient animals, but they live in an environment where increasing fragmentation is occurring. So, looking at a finer-scale view within the Peninsula, I suggest it is important to try to retain what habitat connectivity remains- not just for caracals, but for the many other species that are making it in the urbanizing landscape.
But panning out to the bigger picture– what about outside of the Peninsula? Urbanization is the principle threat to global biodiversity conservation. How can we use the teachings of Tyger and Azure to ensure we protect species beyond the Peninsula? Planning ahead is the answer. Urbanization and habitat loss and modification is going to continue, and is is proceeding at a very rapid pace globally. Looking to the future, it is important that if we want to try to protect biodiversity in the changing landscape, we protect areas that animals can move through to maintain functional habitat connectivity in fragmented landscapes.
Another reward from Tyger
Tyger's collar reached the end of it's battery life in mid-March, and so I was able to send a signal remotely, through a web interface, to the radio-collar to fall off. But as researchers, we do all we can to recover the radio-collars for several reasons. The "drop-off" activation through the website has proven effective on other caracal studies in South Africa, but it doesn't always work. We don't want the caracals stuck with radio-collars for the entirety of their lives, so we attempt to recover the collars to ensure it has indeed fallen off of the animal. The Urban Caracal Project field team followed up to recover the collar in the areas where Tyger's radio-collar collected data. But with no luck, and after days and days of driving around trying to hone in on a radio-signal that should be emitted if the collar indeed has fallen off! And so, I thought that perhaps more effective would be to try to schedule a flight over the area to listen for the collar from above. We frequently try to get to high places when listening for the collars so we get more reach, and by flying you get pretty high!
While the drama of recovering Tyger's collar has been unfolding, I of course happen to be in the United States moving the genetics component of the project forward. So I felt impotent to help with locating Tyger's radio-collar, and decided to put a call out to our Facebook community to ask for help. I posted a plea on Facebook after dinner one Thursday and went to bed holding thumbs something would come through. With the time difference, the post would've gone up in the middle of the night Cape Town time. I happened to wake up earlier than I wanted the next morning– around 5am. But what a surprise awaited me! I checked in with my team and to my surprise, the project field team manager, Joleen, was jumping on a plane in that very moment!!!! What quick response from the community! I've told this story to all of my colleagues in the U.S. and everyone is amazed (and so jealous)! Daily, with these cats, I find myself counting my blessings to be doing the work in Cape Town where there is such a supportive community that has helped this project, surviving on a shoestring budget, thrive.
So what a big thanks we want to extend to The Morningstar Aviation Club and airfield, to Ross Leighton for helping to organize and for sponsoring the fuel, and to Stephan Moser for donating an hour and a half of his time to fly! We weren't able to find the radio-collar, but we did all we could. We believe the collar fell off of Tyger and has gotten buried in sand where the signal is just too hard to hear. The good news is that if it were still on him, we would have most likely hear the signal after weeks of driving around and with the flight.
So while we are giving thanks, I'd like to also extend to Matthew McCarthy, who recently had a birthday (Happy Birthday!). And instead of gifts, he asked his friends to donate funds to buy the project a new GPS unit that we desperately needed! Thank you thank you thank you to Matthew and his friends!
But as always, we still have a list! Our interns have settled in a new house in Glencairn and so we have an updated wish list for the project. If anyone has any of the following they'd be willing to part with, we'd be so grateful! Give us a call at 079-837-8814 or email email@example.com
* A stove for the house- right now the kitchen is set up for electric stove, but used to have a gas line if a gas stove is available
* A refrigerator (our team is growing!)
* A dining room table
* Warm blankets and duvet covers for the coming winter
* Drawers for the bedrooms
And general project needs:
* Small digital camera for investigating caracal diet (simple and old will do!)
* Protective case for GPS units and small digital camera
* SD card reader for our field computer that's old and finicky
* External hard drives for data storage
So thanks as always from the Urban Caracal Project Team. You guys are the fuel that keep us running! http://www.urbancaracal.org/support/