Rattlesnakes: Reproduction

Ten Things I Like About... Podcast

Summary: How do rattlesnakes make baby rattlesnakes? You might be surprised! Join Kiersten as she gives you a rundown of rattlesnake reproduction.

For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean

Show Notes:

America’s Snake: The Rise and Fall of the Timber Rattlesnake by Ted Levin

Rattlesnake: Portrait of a Predator by Manny Russo

Music written and performed by Katherine Camp

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

This episode continues rattlesnakes and the third thing like about them is their reproduction cycle. There are definitely a few things you probably didn’t know about rattlesnake reproduction, for some of you it may be more than a few things, and these facts will throw you for a loop.

As we learned in last weeks episode, most rattlesnakes live in temperate regions, which means they live in habitats that have both a cold season and a warm or hot season. This is important because breeding season is kicked off by warming temperatures and the basking behavior that this encourages. The timing of this activity will vary depending on species but many species will breed in spring and summer. Some will mate in fall and we currently believe this is triggered by the shortening of daylight hours.

After the snakes have had a bit of time to warm their bodies they shed, when it’’s breeding season females will release pheromones at the same time as this shed that indicate she is ready to mate. Males, once they have warmed up enough to move around, will follow those pheromones until they find the female.

If she’s alone, the male will begin the mating ritual. First he’ll rub his chin along her head and flick his tongue gently along her back to entice her to accept him. If she doesn’t slither away, he’ll rub his body along hers, and if all still continues to go well for him she will raise her tail and give a little wave. He’ll line his cloaca up with hers so he can use his hemipenes to deposit sperm in her cloaca. The cloaca is the opening at the base of the tail where snakes do everything that entails things coming out of the body or going into the body. Mating rattlesnakes may be connected in copulation for up to three hours.

If an uncoupled female is not alone when one or more males find her, the combat dance may occur. The two males will quickly race toward each other with their heads raised. They will entwine their necks and raise their bodies up vertically. They can push themselves up almost 1/3 of their body length. When they get too high they both tumble and untangle. Then the dance begins again. The two males will continue to ‘dance’ with each other until one of them tires, is forced to the ground, and slithers away. This combat dance can last up to thirty minutes.

Typically, fangs are never used during this combat dance. Most often the larger of the two males will win, but not always. This can happen without the presence of a female, sometimes two male snakes searching for females that encounter each other may just fight because they’re in the same vicinity.

Once sperm has been successfully transferred, the female can store that sperm for up to a year in a specialized structure in her oviduct. She’ll keep the sperm through winter hibernation until she can produce eggs that will then be fertilized by the stored sperm. This ensures that the eggs will mature at just the right time of year for the young to be born when the temperatures are warm and food is available for the young rattlers.

It occurs to me that I’ve been talking about warm temperatures being important for reproduction. Warm temperatures are actually important for all reptiles for any activity. Reptiles are ecotothermic which means they are reliant on the temperature in the environment to maintain their own body temperature. Too hot or too cold and a reptile cannot function.

Female rattlesnakes are ovoviviparous but are often referred to as viviparous in research papers. What do all these big word mean? Ovoviviparous means they incubate eggs inside their body and the young are born live. Viviparous means to give live birth, like most mammals. So technically both definitions apply to rattlesnakes.

Females will incubate the fertilized eggs in her uterus. For about three months she’ll carry her offspring. During this time she’ll stop eating because as the embryos grow they take up more and more room in her body. It prevents her from swallowing prey whole because there isn’t enough room for her to carry around an intact mouse while it slowly digests and her offspring. The number of embryos will vary from specie to species. Larger species can carry and birth more young than smaller species. An average number across all species can range from two to twelve, give or take.

As the pregnancy progresses, the female will become more and more secretive and sedentary. She’ll move in an out of warm areas to ensure proper incubation temperatures for her eggs but she won’t go far. She will continue to drink water, but she and her young will survive on the fat stores that she stocked up on before fertilization occurred. The embryos are enclosed in a fetal sac or soft bodied egg with a yolk inside while in her uterus. They are attached to the sac through a primitive umbilical stalk. Some materials and gases are passed through this stalk similar to a mammal’s umbilical cord. When she is ready to give birth, she’ll find a secluded place and her young are born looking like a little version of their mother.

This next step is the one that will throw you for a loop. After her babies are born the mother and her young stay in the nest together for almost a week. She does not kick her babies out into the world to fend for themselves. We think of most reptiles being very hands off parents, but rattlesnakes are not like that.

The mother and the newborns stay together in the den until the young shed for the first time, usually about seven days after birth. During this time, we’re not exactly sure what information is passed back and forth between parent and offspring and between siblings, but scientists think this is an imprinting period. The young may be memorizing their mother’s scent so they can follow it back to denning sites later. The shocking thing about this, not so much to me but scientist and other people, is that rattlesnake mothers actually take time to make sure their offspring are protected during an extremely vulnerable time. She’s giving them a chance at a successful life.

Once the young have shed, everyone leaves the nest and goes on their separate ways. Growth rates will depend on available food and the environment, but if they’re lucky they can double their size in three or four months. Small rattlesnakes do have to worry about predation. Other snakes, hawks, owls, coyotes, and feral cats are all threats to neonates.

Depending on species, males will typically reach sexual maturity at two years while females will reach sexual maturity at three years. Females will generally only give birth to young two to three times in their entire life. They take several years in between clutches because it’s quite a strain on their system to lose the weight during pregnancy. It may take them two to three years to get back up to fighting weight.

That is all for this fascinating episode on rattlesnake reproduction. Thanks for joining me on this crazy ride because it’s my third favorite thing about this beautiful reptile.

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Join me next week for another episode about rattlesnakes.

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.