Spring is in the air along with alligator mating season

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Posted: Thursday, May 1, 2014 6:08 pm

Spring in the swamp has arrived, evidenced by interesting sounds and activities in the fresh waters of south Florida - gators are courting.

Mid-April to May is their primary mating season. During this time, visit a national or state park that is home to alligators and look and listen for mating signs. The alligator has a unique courting ritual that delights many a visitor to south Florida.

Males are the showiest of the species as they advertise their availability and interest in mating by head slapping, vibrating their torso, bellowing and jaw snapping. Females also join in with a sound more like a bellowing growl without all the fanfare of the males.

American Alligator - Myakka Park (3).jpg
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The alligator bellow sounds are similar to a motorcycle starting up in the distance.(If you’d like to hear it – visit the Everglades website for an audio link). Though bellowing alligators may be heard year round, during courting season it’s stepped up significantly.

Another mating ritual is the male Alligator head slapping that is often accompanied by series of interesting attention getting techniques unique to this large reptile. First is to look impressive through an elevated posture – where they hold their body straight and somewhat elevated so that much of the body is above the water surface, sometimes they’ll hold this pose for more than 30 minutes! If he’s really showing off the impressive head slap on the water could be followed by a very loud snap of the jaw and then conclude his show of prowess with a guttural growl.

The bellow and head slap are an integral part of the social communication of adult American alligators. It’s a community experience; once one begins others respond with a head slap or bellow, joining the alligator chorus. This unique way of advertising availability seems to be pretty effective for the males of this species as it isn’t unusual to see them surrounded by up to four females during the peak of breeding season! As in other species, some females aren’t impressed with the male’s show and may opt to swim away with a bellowing growl, signaling their lack of interest in furthering this courtship.

American Alligator - Myakka Park (5).jpg
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An interesting difference in the bellows of males and females is the males’ sub-audible vibration just prior to his bellow that produces an infrasonic signal so powerful that water “dances” up around his torso. This vibration can be so strong that anything nearby vibrates as well. If you see this water dance you can be sure it’s a male, as females don’t produce this additional courting signal.

Signs of a mate selection pursuant to all the courtship signals could be spotting two alligators swimming together, one longer than the other, or perhaps they touch each other’s snouts or are blowing bubbles. This new gator couple may lie next to each other on a bank, circle each other in the water, and rub each other’s backs for several days. Their courtship is lengthy for the animal world, often extending 6-8 weeks and copulation occurs underwater and may be repeated a number of times over this time period. It is interesting to note here that alligators (crocodilians in general) are actually very promiscuous. Males and females may have multiple partners during a courting season and a single clutch of eggs may have multiple paternities.

After courtship, and often with the advent of the rainy season, the gators disperse. The female alligator switches gears changing from companion to engineer. In June or July, she seeks just the right location to build her nest. Water levels help her decide the height for her nest site so it won’t be flooded. The location she chooses may be a few feet (1 meter) to as much as 50 feet (15 meters) from the water.

Female alligators use their whole bodies to construct the nest mound. She uses her belly and tail to clear an area and her jaws to tear out and drag plant material to pile into a mound. She mixes the vegetation with sticks, leaves, and mud. As she piles the vegetation, she also compresses the materials she has gathered, making numerous collecting trips. She may construct the nest in a few days or work on it intermittently for a month. The mound is built as much as six feet (2 meters) across and up to a height of three feet (1 meter).

As she finishes the nest building, she may crawl off the mound and circle it a number of times, lifting her head to inspect her work. She then climbs back on the mound and spends several hours slowly turning as she uses her hind legs to create a foot deep (30 centimeter) depression in the top of the mound. She then deposits 20 to 50 oval eggs. Finally, she makes a number of trips back to the waters’ edge to gather muddy vegetation to pile in and over the depression and finishes by compressing the area with her body.

During the 65 day incubation, females stay close to their nests. Some actively defend their nests from marauding raccoons and other animals by lunging and hissing when intruders approach. (For your safety, alligator nests should never be approached.) However, the female alligator may get hungry during incubation and leave the nest to hunt. It is then that female red-bellied turtles may visit the mound, depositing their eggs in the alligator nest. Thus when the female alligator returns she is unknowingly protecting the eggs of both reptilian species. As the alligator embryos develop, it is the heat in the nest that determines the sex of the baby gators. A temperature of 91 degrees F (33 degrees C) or higher produces males, while a temperature of 86 degrees F (30 degrees C) produce females. In between the two temperatures there is a 50-50 chance of either males or females being born.

Silver Springs
Photo by Bill Combs of two baby alligators on a log in the river.

As incubation is completed, some of the hatchlings begin producing a grunting sound, which stimulates the other hatchlings to also grunt. The sound draws the female alligator and she carefully begins opening her nest. The six to nine-inch long hatchlings use an egg tooth to tear through their leathery shells and then head for the water. If necessary, the mother alligator may help the hatchlings emerge by rolling eggs gently in her jaws.

The hatchlings yellow striping provides camouflage as they spread out in the grasses of marshes or along riverbanks. On sunny days, young may climb onto the back of their mothers, using her as a source of warmth. The young may stay with their mother for two years before they begin to disperse.

Alligators in the Everglades grow slowly, but once they reach six feet (2 meters), the cycle repeats with new pair bonds forming and females constructing their first nests as their mothers before them have done for years.

Isabel Kalafarski is a Park Ranger Big Cypress National Preserve. Linda Friar, Chief of Public Information for Everglades and Dry Tortugas National Parks contributed to this article.

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