(Submitted by friend of the blog, Spencer Marks)

A few years ago, I was driving home, and saw something moving in the middle of the street on the north end of the block that my house was on. When I got close enough, I realized it was a 12” California Desert Tortoise just walking down the middle of the street, in broad daylight, and in the middle of the city! Not wanting him (I knew it was male due to the “fighting fork” under his carapace) to get run over, I picked him up, and took him to my house. He seemed very comfortable around people, since when he would see someone approach, he would actually run toward the approaching person (well, as fast as a tortoise can run!), presumably to get fed. I figured he must have been hand-raised, since he had absolutely no fear of humans at all, and seemed to enjoy their company.

A month later, I was talking to a friend (one I didn’t talk to that often), about him coming to pick up some equipment from my house, and he asked for my address. As soon as I gave it to him, he said, “Oh wow … I grew up on that very street … just at the other end of the block from you!” We then talked a bit about who was in the neighborhood when he was growing up, and who still had a house there, and all of that sort of stuff, and for some reason he said, “I had a pet tortoise when I was a kid, and we couldn’t find it when we moved out, so I wonder if it is still at that house…”

I almost fell over! I told him that I had just found a tortoise in the street DIRECTLY in front of his old house the month before. He had moved away over 30 years prior to that, so I assumed it MUST have just been a different tortoise, but when he came to my house to pick up the equipment, he took one look at the tortoise, and said, “YEP! That’s him!”

I asked him if he wanted him back, and he said no, so today “Speedy” lives with me at my new house, with lots of places to roam, and spoiled with fruits and veggies by all who see him!

[EDITOR: We’ve all heard the crazy story of the dog or cat that manages to track their family ALL the way across the country to their new home (and seen plenty of movies about it, too). But it takes the brilliant staying power of a tortoise to stick around and wait 30 years for their family to return to them.]

Updated 4/23/2012

Below are the extended notes provided by Barbara Drescher for use in Skepticality Episode 181. Take a look and leave your comments below.

In most of the stories of coincidence we share, the proximity, time-wise, of two incidents is short, but it’s hard to be shocked by it. Given the number of people with which Spencer was likely to interact in the weeks following finding the tortoise and the likelihood that some of those people lived in that neighborhood at some time in their lives, interacting with the tortoise’s previous owner is less unusual than it appears. The tortoise coming up in conversation is not that unusual, either. Any mention of where Spencer lived was bound to spark a conversation about the fact that the friend once lived there and that topic is likely to spark memories of the pet left behind.

If the tortoise was an adult when it was lost by the friend, the odds were pretty good that he would still be there 30 years later. The three biggest questions that spring to mind are:

  1. What is the probability that the tortoise would remain in that location for 30 years without intervention?
  2. What is the probability that the tortoise would have been moved (or taken in and cared for as Spencer did) by someone during those 30 years?
  3. What is the probability that the tortoise would still be alive after 30 years?

That the probability that the tortoise would remain in that location is high is fairly obvious to most people, I would think. It would take a tortoise most of day to travel even a mile, so tortoises tend
to maintain a rather small home range. Being removed by a new resident or other human requires being seen. Despite his size, which is not insignificant, the tortoise managed to be lost in the first place (assuming it was an adult at the time). The species is known for borrowing, so it is highly likely that he dug a hole under the house and spent much of his life there, undetected. Raccoons, larger and more active animals, thrive in urban areas and are rarely seen by their human neighbors. What’s more, the desert tortoise lies dormant during colder months, reducing the amount of time it is visible even more. I also wonder how many people would even know what to do if they saw a tortoise walking across the road. Unlike Spencer, I would not have known the species or sex of the animal, nor would I know whether it was safe to pick it up. I might simply try to hold traffic until it was safely across the road, then let it be.

If they survive to become adults, the lifespan of a tortoise is similar to that of a human, so 30 years is not unusual at all. The tortoise’s survival, therefore, relied on its ability to find food and avoid predators. Since their diet is mostly grasses, we are left with predators as the biggest danger. More specifically, ravens and coyotes (since gila monsters, badgers, and foxes are rare in this tortoise’s location). If, as I’ve assumed, the tortoise was an adult when it disappeared, it is fairly safe from these as well. Ravens will eat tortoise eggs and juveniles, but the shell of an adult is usually too much work when other food is more readily available. Although there might be some overlap in the daily cycle of the coyote (which tends to retreat to its den when the sun rises) and the desert tortoise (which is most active in the first half of the day), again, the tough adult shell makes a tortoise less desirable than other choices. In short, the chances of surviving 30 years on its own are excellent, assuming (again) that the tortoise was an adult when it was lost. It’s actually quite small if it was very young. Only 1 in 5 survives to adulthood in its natural habitat.

When we consider all of the factors, the one which brings the probability of this incident down the most is the temporal factor – the order and proximity of the events in time. It is certainly considerably lower than the average participant’s chances of winning a football pool at their office. Still, it is much greater than that of my next door neighbor winning the California lottery, yet that jackpot is won by someone’s next door neighbor dozens of times each year.