RE: NANFA-- How Big is that Alligator ?

Hoover, Jan J ERDC-EL-MS (HOOVERJ_at_wes.army.mil)
Fri, 1 Nov 2002 16:18:03 -0600

Assuming the gentleman in the picture is 200 cm (6 ft.) tall and that he is
standing directly behind the alligator, the alligator should be
approximately 600 cm (18 ft) total length (TL). This would be just a little
smaller than the 19-20 ft figure traditionally accepted as maximum known
size and a lot bigger than most alligators for which size is reliably
documented. The largest alligator in Florida taken during the period
1977-1994 (N = 76,670 !) was only 427 cm TL (14 ft) and only six other
specimens even approached that size (> 400 cm); most were < 305 cm (< 10 ft)
and the largest alligator for which a skull exists is only 454 cm (14.9 ft
TL)(Woodward et al., 1995). If this alligator were truly larger than 16 ft,
it would be newsworthy and well-documented. I believe that it must be
considerably smaller.

I tried three different techniques to estimate size but all assumed that the
duct tape around the snout is three bands wide (15 cm). This was a
conservatively high estimate which I used as a unit of measurement. I also
used some measurements that I made this afternoon on a local alligator. A
similar approach was used recently to estimate the size of the goblin shark
recently captured in the Gulf of Mexico.

1. I used calipers set for the width of the duct tape and walked them 21
times from the tip of the tail to the tip of the snout: 315 cm (10.3 ft).
This is probably an underestimate of the alligator's true size since the
front half of the alligator is turned at an angle to the camera.

2. I did the same from the tip of the tail to the insertion of the hindlegs
and came up with 217 cm (7 ft). That measurement on a 90 cm TL alligator,
is 54 cm. Using the 54:90 (tail:total) ratio, I extrapolated TL for the
alligator in the picture at 362 cm or 11.9 ft. I think this is a reasonable
estimate.

3. Lastly, I used the local alligator's snout-width/TL ratio (1:16), and my
very generous approximation of the photographed alligator's snout width (30
cm) and came up with an estimate of 491 cm or 16 ft. I think this is an
overestimate because of possible allometric growth of alligator heads.
Alligator head lengths track total lengths pretty closely (Woodward et al.,
1995), but don't older, bigger alligators have wider heads ?

Also, there are two things odd about the photo: 1) there's only one (a truly
remarkable animal would have inspired a series of dramatic pictures; 2)
there is no attempt to accurately represent scale (animal photographers are
famous for including coins, lens caps, etc. as visual yardsticks). It would
have been an easy, to place a cinder block or some other suitable object in
immediate proximity to a multiply duct-taped gator and then take several
photographs.

For more information on on how big an alligator is likely to get, see:

Woodward, A.R., J.H. White, and S.B.Linda. 1995. Maximum size of the
alligator (Alligator mississippiensis). J. Herpetol. 29(4): 507-513.

For more information on this alligator photo and a diifernt approach to
estimating its size, go to: http://www.flmnh.ufl.edu/cnhc/18ftgator.html

Bottomline: Big alligators are usually smaller than they appear.
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