Depending on who you talk to, there are up to 7 'groups' of Red-foots.
Functionally, I think there are probably basically 5, with some regional color variation within the 5. This is based on Vinke's South American Tortoises, Pritchard's Turtles of Venezuela, and so forth.
First, we can usually divide the Northerns from the Southerns by the plastron- a mostly light plastron is usually a Northerner, a mostly dark plastron is usually a Southerner.
North-eastern (E. Venezuela to French Guiana): the 'typical' Red-foot. 30-35cm adult length, black carapace background, constricted waist on adult male, yellow/orange/red colors on limbs.
North-western (Panama, Colombia, W. Venezuela): Shell background is more coffee/grey, almost no red coloration on limbs.
South-eastern (East Brazil): This region seems to be home to 2 variants- the 'red' and the 'yellow'.
'Reds' are the 'Cherry Head' variant. These MAY average a bit smaller (22-28cm), but many specimans are a bit larger than average. Reds tend to have very dark necks with bright red or orange colors on it. They tend to show shell mottling more often than others, and seem to have a slightly bulbous red-tip nose (the Rudolph Sign). They rarely show the male wasp-waist, but usually have a distinct hooked scale below the front elbows- almost a 'spur'.
'Yellows' look like North-easterns with yellow coloration and a dark plastron.
South-western (Paraguay and Bolivia): Big- 35-45cm- tortoises, little to no wasp-waist, 'spur' like the South-eastern Reds.
Within the above 5 groups, I think there are some local color variations- but a lot of these variations seem to disappear as the tortoises get older.
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UPDATE March 25th, 2011: Based on DNA research (VARGAS-RAMIREZ, Mario; Maran, Jerome; Fritz, Uwe. "Red- and yellow-footed tortoises, Chelonoidis carbonaria and C. denticulata (Reptilia: Testudines: Testudinidae), in South American savannahs and forests: do their phylogeographies reflect distinct habitats?"), I've modified the types of Red-foots a little:
(Names in CAPS are the terms used in the above article. Names in (parentheses) are the names I use to try to clarify things)
NORTHWESTERN (Panamanian)- Panama and west of the Andes in Venezuela
NORTHERN (Columbian)- Columbia, south of Venezuela. This was not a group that has been discussed widely as a separate group before. They seem to look a lot like the next group.
NORTHWESTERN (Guyanan)- The 'Guyanan Climatic Zone' of mid-Venezuela to French Guiana and bits of northern Brazil
EASTERN (Brazilian)- The 'Cherry-heads' and there yellow-headed but otherwise identical kin from the central-to southern part of Eastern Brazil
SOUTHERN (Gran Chaco)- Paraguay and Bolivia
Research has been showing that a.) these groups have a significant difference in their DNA and that there are barriers of some sorts between the groups to help keep them apart, and b.) that one of the barriers is the Amazonian Basin Rain Forest- Yellow-foots travel freely throughout the Basin, but Red-foots do not enter it to any great extent- the DNA does not drift from group to group.
Not much different than what I posted earlier. The big changes are:
- combine Cherry-heads and the 'yellow heads' as just being normal color variants of Brazilians.
- breaking Columbians into their own group, and
- yet another researcher using some slightly different names for the groups. It would be nice to have agreed-upon names for these groups.
Functionally, I think there are probably basically 5, with some regional color variation within the 5. This is based on Vinke's South American Tortoises, Pritchard's Turtles of Venezuela, and so forth.
First, we can usually divide the Northerns from the Southerns by the plastron- a mostly light plastron is usually a Northerner, a mostly dark plastron is usually a Southerner.
North-eastern (E. Venezuela to French Guiana): the 'typical' Red-foot. 30-35cm adult length, black carapace background, constricted waist on adult male, yellow/orange/red colors on limbs.
North-western (Panama, Colombia, W. Venezuela): Shell background is more coffee/grey, almost no red coloration on limbs.
South-eastern (East Brazil): This region seems to be home to 2 variants- the 'red' and the 'yellow'.
'Reds' are the 'Cherry Head' variant. These MAY average a bit smaller (22-28cm), but many specimans are a bit larger than average. Reds tend to have very dark necks with bright red or orange colors on it. They tend to show shell mottling more often than others, and seem to have a slightly bulbous red-tip nose (the Rudolph Sign). They rarely show the male wasp-waist, but usually have a distinct hooked scale below the front elbows- almost a 'spur'.
'Yellows' look like North-easterns with yellow coloration and a dark plastron.
South-western (Paraguay and Bolivia): Big- 35-45cm- tortoises, little to no wasp-waist, 'spur' like the South-eastern Reds.
Within the above 5 groups, I think there are some local color variations- but a lot of these variations seem to disappear as the tortoises get older.
***********************************************************
UPDATE March 25th, 2011: Based on DNA research (VARGAS-RAMIREZ, Mario; Maran, Jerome; Fritz, Uwe. "Red- and yellow-footed tortoises, Chelonoidis carbonaria and C. denticulata (Reptilia: Testudines: Testudinidae), in South American savannahs and forests: do their phylogeographies reflect distinct habitats?"), I've modified the types of Red-foots a little:
(Names in CAPS are the terms used in the above article. Names in (parentheses) are the names I use to try to clarify things)
NORTHWESTERN (Panamanian)- Panama and west of the Andes in Venezuela
NORTHERN (Columbian)- Columbia, south of Venezuela. This was not a group that has been discussed widely as a separate group before. They seem to look a lot like the next group.
NORTHWESTERN (Guyanan)- The 'Guyanan Climatic Zone' of mid-Venezuela to French Guiana and bits of northern Brazil
EASTERN (Brazilian)- The 'Cherry-heads' and there yellow-headed but otherwise identical kin from the central-to southern part of Eastern Brazil
SOUTHERN (Gran Chaco)- Paraguay and Bolivia
Research has been showing that a.) these groups have a significant difference in their DNA and that there are barriers of some sorts between the groups to help keep them apart, and b.) that one of the barriers is the Amazonian Basin Rain Forest- Yellow-foots travel freely throughout the Basin, but Red-foots do not enter it to any great extent- the DNA does not drift from group to group.
Not much different than what I posted earlier. The big changes are:
- combine Cherry-heads and the 'yellow heads' as just being normal color variants of Brazilians.
- breaking Columbians into their own group, and
- yet another researcher using some slightly different names for the groups. It would be nice to have agreed-upon names for these groups.