Why Do Turtles Stack Or Climb Onto Each Other?

Have you ever seen a bunch of turtles stacked on top of each other? Maybe you’ve wondered why do turtles climb onto each other like that? Perhaps you were walking by a pond one day and saw a log piled high with turtles acting like it was the most normal thing in the world.

Turtles like to stack on each other so both get more UV rays and for warmth. The turtles on the top get more sunlight while the turtles on the bottom benefit from the collective warmth of the stack. Stacking is a natural phenomenon and may offer additional benefits, like protection from predators.

Turtles are ectothermic creatures, which means that they can not control their own body temperature like your standard warm-blooded animal. So to regulate their temperature turtles will utilize their environment, since they cannot rely on their own internal processes.

Because of this they are constantly moving from cooler areas to warmer locales and vice versa. By doing this, turtles are able to effectively control their body temperature.

Your standard pond turtles like the red eared sliders, painted turtles and yellow bellied sliders love the water and love swimming in it. However, the water will cool them down, so to warm up from time to time they will engage in their second favorite activity, basking.

Turtles alternate between swimming and basking to help regulate their body temperature.

By climbing on top of each other or stacking, turtles are able to bask effectively and warm up their bodies quickly, even if there isn’t a lot of basking area available.

By having each other in such close proximity, the warmth of the other turtles through the convection of heat waves makes them warm up faster. Most likely this is not the only reason they do this, there are several other advantages that could be driving this learned behavior.

Turtles Stacking to Protect From Predators

Animals don’t always see the world the way you and I do. Depending on how tall a creature is, many things can look much bigger from a spot closer to the ground. Just like a person can potentially scare off an intimidating mountain lion by spreading their jacket, animals have been known to engage in tricks to form a more imposing figure.

Turtles do something similar when they engage in stacking. For examples, one of pond turtles greatest possible threats are alligators. When they sit on top of each other, they can seem to an alligator like a much more difficult snack. One little turtle on its own might look like an easy grab, but a stack of turtles would be more difficult to deal with. He would have to bite through two or more turtle shells in order to get to any meat. A turtles shell can be extremely tough, tough enough to make an alligator think it might just not be worth it.

Another possibility is that turtles could be using safety in numbers to keep a lookout from up high. More eyes can see better than two after all. If a turtle sees danger and dives off the stack, that would alert the other turtles that danger is near.

It’s important to note that as far as we know, turtles don’t really have a social hierarchy approaching a communal society like a wolf pack. However, by turtles simply doing whats good for them, they help each other.

Location is Everything

This turtle has found some prime real estate, but may be forced to share when his friends show up

Besides safety in numbers, another reason pond turtles like to stack could be all about the location. Ponds can have a lot of water great for swimming, but without a lot of desirable places to bask and dry off. There may be just a few good logs or rocks for a turtle to hang out and absorb some of the suns rays. Turtles love to sun worship, and exactly like avid beach goers (minus the sunscreen) will settle for nothing less than that perfect spot.

So you end up with few spots to bask, but lots of turtles needing to bask. Rather than fighting each other and risking harm to themselves and turtle kind as a whole, they have found a more peaceful manner to resolve it. The turtles can simply chill out while warming up and share with each other by getting on top of each other. Some people have tried to see how many people can fit in a Volkswagen Beetle. So do turtles with their basking logs and rocks.

Faster Access to Body Warmth

Pond turtles, like painted turtles and red-eared sliders, need to dry and warm themselves up to a certain temperature before they can dive back in to the pond. When they stack, their bodies collect the heat of the sun collectively spreading more heat to each other than they might get by themselves.

This then allows them to reach their desirable body temperature faster so that they can get back to swimming and finding delicious treats to eat. You know all the things that turtles just love to do.

Does Stacking Hurt the Bottom Turtle?

So turtles have lots of reasons to stack which seems great, but you may wonder, does all this stacking cause any pain and suffering to poor turtle stuck on the bottom?

Jonathunder / CC BY-SA

Turtles can stack without worry based on their very strong shells

Due to the incredible strength of a turtles shells, having multiple turtles stacked on top of the bottom one does nothing to hurt them. A turtles shell is simply too strong for that. In fact, it would likely take the weight of at least over a hundred turtles to hurt a bottom turtle.

In some ways, the bottom turtle might even have it the best! By being on the bottom he or she gets a lot more warmth than the turtles higher up the stack. Additionally, if there is an alligator attack or an attack by some other creature, the bottom one will be the most protected.

Now turtle bullying can and does take place. But usually this is not in the form of piling on top of each other, it usually occurs through biting. Turtles do not seem to have any concept of body slamming or any wrestling move of that sort. So no need to worry about turtle sumo wrestling, a turtle will simply bite you if he doesn’t like you.

Pet Turtles Stacking in Captivity

Oxlamb / Public domain
Turtles stacking in captivity isn’t necessarily an issue, but could be a cue to adjust your turtles environment

If you have multiple turtles in a single tank, you might find them stacking sometimes. Is this a good or a bad thing?

Now while turtles stacking in the wild is a perfectly normal and even advantageous thing for them to do, in captivity this is a bit more complex.

Turtles, as you may know, need the ultraviolet ray of the sun or indoors we use a UV basking bulb in order to ensure good health and continued prosperity. At least what turtles think is prosperity. Outdoors in the wild, the sun moves through the sky as the day progresses, so that each turtle in the stack gets some good UV rays and not just the one on top.

However, when you are indoors, generally the environment you have set up will not move. It stays in one place, usually shining light at one angle all day. So depending upon how your UV lights are placed, having turtles stack could be depriving someone from getting enough UV rays.

Usually the stacking order changes and doesn’t seem to be determined by any kind of dominance hierarchy, it’s just happenstance. However, if one of the turtles for some reason keeps being on the bottom, it’s possible that they might not get enough UV rays.

Generally, I would say this is not something to worry about that much, but it is something nice to know about in case there is some problem.

If you are worried that one of your turtles keeps getting the short end of the stick in the stacking order, then one solution is to try another UV bulb to spread the size of the basking area. That way the UV lights are hitting from multiple angles to ensure everyone gets that right amount.

Generally you’re going to want to place the two UV bulbs side by side so that the basking area gets bigger. You don’t really want to make two different basking areas as turtles do like to stack so they might just ignore one basking area and keeping stacking under the other one. So simply expanding the basking area as opposed to making two would be the more ideal.


So in conclusion, turtles like to stack so that their bodies can benefit from the collective warmth of the stack. By climbing on top of each other this also helps them to scare off predators and giving more warning before a possible attack. Stacking does not hurt the bottom turtles as their shells are simply too tough for them to be harmed in that manner.

If you have pet turtles stacking then its probably fine. However, if you’re concerned it can be a good idea to add a second UV bulb right next to the first one in order to expand the size of the basking area.

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