Territoriality in Male Wood Turtles

Views:

381 views

On a sunny May afternoon, ice still clinging to the riverbanks, I rounded a river bend and heard a curious noise coming from ahead, just out of sight. Perhaps two large sticks smashing together in the current, splashing water every few seconds or so, or a child playing with rocks in shallow water. Unsure of what lay ahead, I approached slowly, until the scene came into view: two Wood Turtles engaged in fierce combat. In only a few inches of water, the pair had squared off face-to-face, aggressively ramming and biting each other. Moments later, they saw me and bolted in opposite directions. This being part of a Wood Turtle survey, it was my duty to capture them briefly to collect information about their size, age, and health. Both turned out to be old males, and very large. I had just glimpsed the briefest moment of a rivalry that could have started decades ago.

 

 
 
 
 
 
View this post on Instagram
 
 
 
 
 
 
 
 
 
 
 

 

A post shared by Garden State Tortoise (@garden_state_tortoise)

Turtles aren’t generally thought of as territorial animals. Large numbers may live in close proximity, and can be seen basking on top of one another in disorganized piles. While turtles may not defend physical territories, such as basking spots and feeding grounds, males can actually be very aggressive toward one another, especially in peak breeding season. Somewhat famously, tortoises engage in ramming contests, with males of some species possessing a specially evolved protrusion on the bottom of their shell called a gular horn, which they use to flip over their opponents. Less well known is the rivalry between male Wood Turtles.

Although Wood Turtles overwinter in streams, they feed primarily on land and may wander great distances from water in the summer. Females travel farther from streams, sometimes spending weeks on end on land and returning to water for only brief periods until fall. Males tend to stick closer to streams, traveling extensively up and down river channels, sometimes covering miles in a single year. The reason for this difference is simple, and is not unique to turtles: females look for food and males look for females. Even though female Wood Turtles spend much less time in streams, finding them on land is a proverbial needle in a haystack situation, but by constantly moving up and downstream, a male is much more likely to find a female than if he looked for them on land.

In the spring and fall, Wood Turtle breeding is at its peak. We have seen this pair mating more than once, always in September.

Peak breeding season for Wood Turtles occurs in the spring and fall, but the timing may have less to do with biology than it does with simple math. A female turtle can store sperm for several years, so it doesn’t really matter when she mates, and mating does sometimes happen in the summer. In the spring and fall when every Wood Turtle is in or very close to their streams, males and females encounter each other much more often than in the summer, and competition between males is at its greatest.

Almost every adult female will mate several times each year, but only a small handful of dominant males sire the vast majority of young. These dominant males maintain their hierarchy by bullying and chasing away their rivals, putting great effort in keeping them away from females, especially during the breeding season. When we witness such disputes, it is usually between a dominant individual and a juvenile or young adult. These fights appear very one-sided, with the alpha chasing the other turtle away, biting at his tail, feet, and shell. When two dominant males square off, the fights can be quite spectacular, but this is rarely witnessed in the wild.

Established pecking orders can last a long time, as Wood Turtles live for many decades, and old rivalries may play out between the same turtles year after year. As far as we know, combat between male Wood Turtles rarely results in serious injury in the wild. The topic is not well-studied, and those lucky enough to witness Wood Turtle combat usually only capture a snapshot of how these rivalries play out. Twice I have chanced upon large males in dispute, but my presence disrupted the behavior on both occasions. Try as we might to learn about the full ecology of these animals, the mere act of looking can change what we see. Fully witnessing the process of two high ranking male Wood Turtles beginning and ending a territorial dispute is something that very few people, if any, have seen in the wild. If you are one of the few, count yourself among the very fortunate. Seeing the most primal aspects of nature is something to cherish.