Transcript AMERICAN ALLIGATOR Alligator mississippiensis

AMERICAN ALLIGATOR
Alligator mississippiensis
IDENTIFICATION
• One of the largest living reptiles
• Has a large rounded body with thick limbs
• Size:
Adult males: avg. length 13-14 ft, occasionally up to 16 ft,
weight 400 – 500 pounds
Adult females: avg. length 8 – 10 ft and weigh 160 – 230
pounds
• Both sexes have “armored body” with a muscular
flat tail
• Nostrils located on the upper end of snout for
“submerged breathing”
IDENTIFICATION
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ALLIGATOR
• CROCODILE
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Broad head – blunt snout
Lower teeth do not show
with mouth closed
Black in coloration
Prefer fresh water
• Narrow head- long snout
• Lower teeth visible when
mouth is closed
• Brown in coloration
• Prefer salt/brackish water
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Alligator mississippiensis
Crocodylus acutus
LIFE HISTORY
• “Living Fossil” from the Age of Reptiles
• Has survived for over 200 million years
• Market Hunting and Habitat Loss
depleted them from most of their natural
range (est. 10 million skins taken)
• 1967 placed on Endangered List
LIFE HISTORY
• USFWS, State Agencies, and concerned
stakeholders joined forces
• KEY TO RECOVERY – multi-discipline
management practices
• 1987 removed from Endangered List
• Today – widely distributed and numerous
throughout most of it’s natural range
• Listed as Threatened due to:
- American crocodile listed as Endangered
- Listed on CITES: Appendix II
- IUCN Red List: LRIc (low risk, least concern)
RANGE & POPULATION
• National population: > 1 million naturally occurring
• 150 active farming operations
• Natural Range: Central America and Southern United
States to include; Alabama, Arkansas, North & South Carolina,
Florida, Georgia, Louisiana, Mississippi, Oklahoma, and Texas.
ECOLOGY
• HABITAT
- Primarily freshwater edges around
swamps, marshes, rivers, lakes, and ponds.
- Will venture into brackish or salt water
for short periods, lacks the buccal ( salt
secreting gland) found in crocodiles.
ECOLOGY
• FEEDING HABITS:
- Carnivorous, opportunistic feeder, will eat anything it
can catch.
- Hunts primarily in water – will take small mammals at
waters edge.
- Eats small prey whole – large prey is drowned
(tenderized) then eaten in large pieces
- Have a specialized valve (glottis) allows for catching prey
underwater
- Feeding activity ceases if water temperature falls
below 20º to 23ºC (68-73ºF)
ECOLOGY
• FEEDING HABITS:
- Preferred Foods
Adult: fish, turtles, wading birds, snakes,
frogs, carrion, and small mammals.
Juvenile: small fish, crustaceans, snails,
shrimp, tadpoles, and frogs.
- Food for: juveniles are preyed on by snakes,
raccoons, wading birds, large fish,
otters, osprey, and other alligators.
- Consumption: adults consume 20 lbs of meat per week
in warm weather – 0 lbs during winter
ECOLOGY
• BREEDING HABITS:
- Breed annually in April and May
- Mating occurs in open waters at night
- Males and females reach sexual maturity
at 6 ft, in length (10-12 yrs of age)
- Males roar to attract females and ward off
other males
- Mature males establish a territory and will
service up to 10 or more females and will
defend the territory against intruders
ECOLOGY
• BREEDING HABITS:
- Once breeding occurs the female will seek out a secluded
location and construct a large mound nest out of muddy
vegetation
- 1 wk later female lays 30-70 eggs (Jun-Jul)
- 60-65 day incubation period
- young hatch with aid of egg tooth
- the young immediately signal mother with high pitched
grunts
ECOLOGY
• BREEDING HABITS:
- Mother will then open the nest and gently
carry the young in her mouth to water
- Females tend to their young up to 3 years
- Young are born 6-9 inches long and have
yellow bands for camoflage
- Approx. 80% of the young fall to predation
ECOLOGY
• PHYSICAL ADAPTATIONS:
--Large strong jaw has 80 teeth, and is used to
capture, crush, and dismantle
--Cannot chew – must swallow food whole or in
large chunks
--Eyes, ears and nostrils are near top of head, with valves
to close ears and nostrils when sumerged. This allows
the alligator to be able to submerge its entire body and
still breath
--Can stay submerged 45-60 minutes
--Toes are joined at base by webbing
--Good binocular vision
ECOLOGY
• LOCOMOTION:
-- Moves efficiently in water, swimming
with serpentine movement of body and
tail, uses hindfeet as rudders
-- On land, slides on its belly, walks or
gallops for short distances
• HEAT REGULATION:
-- Ectothermic
-- Lies on the banks to bask in sun for warmth
-- Submerges in heat of day to cool off
ECOLOGY
• ENVIRONMENTAL ADAPTATIONS:
-Denning: alligators create dens to survive the dry season
and winters – accomplished by digging tunnels
into over hanging banks
- Icing response: Alligators can survive freezing
conditions if they are in water, they submerge
their bodies—but keep their nostrils exposed.
When the surface freezes they can still breathe.
Essentially their upper body becomes trapped in
ice. Testimony to their survival ability.
TAXONOMY
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Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertbrata
Class: Reptilia
Order: Crocodilia
Family: Crocodylidae
Subfamily: Alligatorinae
Genus: Alligator
Species: alligator mississippiensis
ECOSYSTEM ROLE
• “KEYSTONE SPECIES”
-- Controls populations of prey species
-- Creates peat beds (old or abandoned nest)
providing for Red-bellied turtle
(Chrysemys nelsoni) nesting sites
-- #1 Value “Gator Holes” fill with water during
rainy season and hold water well into the dry
season – creating miniature wetlands that
provide critical habitat for a variety of species
ECONOMIC ROLE
• NEGATIVE IMPACTS:
-- Threat to humans – in highly populated
areas have been known to eat pets and
small children
-- “Nuisance alligator” programs have been
put into place with good success
• POSITIVE IMPACTS:
-- Tourism $$$$$$$$
-- Hunting revenues – hunted for skins and meat
-- Multi-million dollar farming industry – farmed
for skins and meat
FUTURE RESEARCH AND
MANAGEMENT
• American alligator is the best studied species of
crocodalian
• Research is currently being conducted by private,
industrial, governmental, and educational
institutions in the following areas; population size,
distribution and trends, animal sizes, sexes, activity
periods, growth rates, and reproduction efforts, diet,
nutritional energetics, responses to thermal effluent from
reactors into cooling reservoirs, uptake of radionucleides,
genetic patterns, and the conservation of the species.
SAFETY NOTES
1) Don’t feed the alligators
2) Keep your distance
3) Never disturb nest or small alligators
4) Keep your pets and children away from alligators
5) Don’t swim in areas that are known alligator habitats
6) Be cautious when fishing in waters with alligators