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How Do Alligators Reproduce?

How do alligators reproduce?

Just two species of alligator remain from prehistoric times, on exactly opposite ends of the globe: the American alligator (A. mississipiensis) and the Chinese alligator (A. sinensis). The American alligator is found in the southeastern United States, the majority in Florida and Louisiana.  They primarily reside in freshwater sources such as lakes, swamps, marshes, ponds, and rivers but have been found in marine salt waters.  [1]  Alligators are egg-laying reptiles that reproduce through sexual reproduction.

Alligator Mating Rituals

The mating rituals of alligators reflect the many millennia of their evolution. Late in spring, male alligators will become more forceful about establishing territory. To get the attention of those females, males will slap their heads against the water and make echoing grunts. On other occasions, some groups of the species have large groups of males gathering to grunt in chorus. This is meant to attract females from many miles around. Once they get there, of course, it’s every man for himself.

Alligators Are Intimate?

Once the alligators have paired, the courting ritual begins.  The two will swim together, touch noses, and blow bubbles in the water. [2]  The male alligator fertilizes the eggs inside the female with a very mammal-like phallus that’s usually kept inverted inside its cloaca.  [3]

Interestingly, a new study has discovered that many alligators display loyalty to their mating partners.  In the ten-year study, scientists found that up to 70% of female alligators choose to mate with the same partner over the course of many years. [4]

Where Do Alligators Lay Eggs?

Generally within a month or two, the female alligator will then begin to locate a suitable spot to lay her eggs. [5] She makes a bed of vegetative matter with her hind legs, lays her eggs in the center, then covers them liberally with more vegetation. Called a clutch, she will lay between 20-60 eggs depending on her age and health. The average clutch size is between 35-40 eggs. [6]

Through mid-summer, the eggs will be kept warm by the gasses produced by the rotting vegetation. Falling victim to predators and weather, fewer than 70% will survive. [7]

Temperature-Dependent Sex Determination

The sex of many reptiles, such as snakes and lizards, is determined by sex chromosomes at the time of fertilization.  The sex of the alligator, on the other hand, is determined by environment.  During development, the temperature of the eggs will determine what sex the alligator will be.  Lower temperatures of 86°F or below will produce a female alligator, while temperatures above 91.4°F will produce a male.  Temperatures in between will produce both male and females. [8]

How Do Baby Alligators Hatch?

In about sixty days, baby alligators are ready to hatch.  They first give out a sound called a yerp to alert the mother that they are ready to hatch.  The mother will then remove the nesting material to expose the eggs.  The baby alligators, called hatchlings, are now ready to break through the egg with an egg tooth, which has developed on the tip of their snouts for this purpose.  The egg tooth will disappear within a few days.  If the hatchling cannot free itself from the shell, the mother will roll the egg in her mouth until it cracks, freeing the hatchling. [9]

The Reproduction Cycle Begins Again

The hatchlings live in groups called pods and are aggressively guarded by their mothers for the first two years.  Even under this protection, nearly eighty percent of hatchlings fall victim to predators such as birds, raccoons, snakes, and even other alligators. [10]  By year six, they will have reached maturity, but their sexual maturity develops in relation to their size.  Both male and females reach sexual maturity when they reach six feet in length, which is usually between years 10-12. [11] At this time, the mating ritual begins again.

 

Resources

[1][2] [6] [7] University of Florida IFAS Extension
Living with Alligators a Florida Reality
http://edis.ifas.ufl.edu/uw230

[3][5] eNature; Burton, K
Alligator Egg Fertilization
http://www.enature.com/expert/expert_show_question.asp?questionID=18700

[4]Wiley News Press Release
Loyal Alligators Display the Mating Habits of Birds
http://www.alphagalileo.org/ViewItem.aspx?ItemId=61720&CultureCode=en

[8] [9] Southern Regional Aquaculture Center-Texas A&M University; Masser M.
Alligator Reproduction-Breeding and Egg Incubation
https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/42/

[10] [11]Smithsonian National Zoological Park
American Alligator Fact Sheet
http://nationalzoo.si.edu/animals/reptilesamphibians/facts/factsheets/americanalligator.cfm

National Geographic
American Alligators
http://animals.nationalgeographic.com/animals/reptiles/american-alligator/

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