Eye trait in males.

[matt41gb]

Over the years I've noticed that a lot of "Northern" males eye differs from the females eye. The female's eyes seem to be completely black, but the male's pupil and iris are centered with lighter tissue surrounding it. I've seen this trend on several occasions and have never seen it documented. Maybe I'm on to something?? You may be able to tell the sex of a young red-foot just by the eye.

These are pictures of two different Northern males. Both tortoises have that particular look to their eye.

Male #1

Male #2

This is a young red-foot, maybe only a couple of years old. Not close to sexual maturity, but has the same eye pattern displayed in the two older males.

Northern females showing eyes that are completely black.

Also note that the male's faces seem to have a sort of "scowl" on them, while the female's are softer. I haven't noticed this in every case, but it seems to be the trend. Let me know what you guys think.

-Matt

 

[HarleyK]

I have also been wondering why my 3" rf has that outlining around its iris (I think it is the sclera) and I have been comparing pictures also. Curious as to what other people think!

 

[Redfoot NERD]

Males -

Females -

'05 Female -

'05 ? [ males ] -

You may be on to something Matt.. although hatchlings - 2 year olds look virtually identical.

 

[Shelli]

This is very interesting! The one thing that I noticed about the difference between my two RF's I have owned although very young was the eyes...
I will have to compare more pictures that I have of Olive... Olive also seemed to have a narrower bridge between the top of her eye and top of her head.. maybe she was a he... her pictures she always looked a bit cross... LOL..
Where as Jaba looks more soft and baby in pictures even though Jaba is roughly the same age as Olive if not a little older.

 

[PeanutbuttER]

Hmm, this is cool. I wonder if it turns out to be true across all the subspecies as well.

 

[matt41gb]

Thanks for the pictures NERD. Maybe this is a good way to tell gender at a young age. I guess more research will have to be done on it.

-Matt

 

[Redfoot NERD]

Thanks for the pictures NERD. Maybe this is a good way to tell gender at a young age. I guess more research will have to be done on it.

-Matt

Does research mean more examples at younger ages until they grow up? How would you research this?

 

[Madkins007]

Thanks for the pictures NERD. Maybe this is a good way to tell gender at a young age. I guess more research will have to be done on it.

-Matt

Does research mean more examples at younger ages until they grow up? How would you research this?

We would need to find a lot of examples of the eye difference from as many tortoises as we could, from as many sources as possible, then track them to adulthood to see if there is a correlation between the 'ring' and gender.

We need a wide sample to help figure out if it is a blood-line issue, a regional issue, possible evidence of a subspecies, caused by foods or cares, influenced by region or habitat, etc.

If we identify 100 young'uns with the rings and 100 without from across different collections and locations, and track them to full 'no doubt about it' adulthood, we can look at the numbers and tell for sure.

If ALL of the rings turn male, and none of the others do, then it is pretty much a given. If 50 turn male, and 50 of the no ring do too, then it is random.

It will probably be somewhere in-between, though- something like 80% of rings turning male, and 15% of non-rings turning male. We could then say that there is about an 80% chance you can predict by the ring- which would be a big boost over what we know now.

Nice catch, Matt!

Let's see- the black 'hole' in the middle of the eye is the pupil. The colored part around it is the iris, the 'white' is the sclera. What do you think? Is the 'ring' a lighter iris, or are the tortoises showing the sclera? It looks to me more like the sclera.

Question- might we be seeing an artifact, a false result from being photographed? Opening the eye more widely because someone is shoving a camera at them?? Males somehow feeling more threatened than females maybe?

 

[matt41gb]

Well said Mark! I just got home and am catching up on the forum posts. Maybe others could post pictures of their young red-foots that have grown into maturity, before and after pictures. That would be a good way to put this to rest.

-Matt

 

[shane1111]

out of my 2 hatchlings and a yearling only one has that yellow ring. and its my little Blonde Red Foot that has the yellow ring both my cherries have brown.

 

[Madkins007]

The other thing we would need to verify is if the same torts consistently show or do not show the ring.

I looked over my archive and cannot see the eyes clearly enough often enough to say anything one way or another.

 

[Madkins007]

Matt's and Terry's torts may just be a statistical fluke. Another keeper/breeder told me in an email that the eye rings in their collection are more randomly distributed and that they do not see any pattern in gender, locale, etc.

Anyone else with a buncha Red-foots? Pattern, random, what?

 

[Laijla]

Interesting topic. I have just one northern that has a dark 'soft' eye and a rather placid nature. It is only a year old so time will tell if turns out female. The tort's with the 'halo' around the iris do have a more serious, intimidating look --- if it were to be a more typical male trait seems that might be to their advantage?
Laijla

 

[matt41gb]

I wonder that if it is it's a true dimorphic trait, that subtle area of the sclera could be some sort of way for males to distinguish gender as well. It could possibly serve as a warning to other males, or may be attractive to females. We will have to see hundreds of examples from hatchling to adult to really know this since there isn't any known documentation of this in the past. Maybe we'll get some more people to post some of their examples on here. At least we'd get a better idea until it's really confirmed by the experts.

-Matt

 

[HLogic]

It certainly is polymorphic, much like our eye color, but from the evidence it is not sexually dimorphic (i.e. two different traits expressed by opposite sexes).

Female Brazilian 3
Female Brazilian 4
Guyanan Female 1
'Paraguayan' Male 1

I'll try to get more pics of the other eye colors in the crew...

 

[jackrat]

My antique male Northern has a totally dark eye.

 

[travisc]

i have a 8 year old female red foot that has the blue ring around the eye ill try to get i pic of her so i can post it

 

[EricIvins]

Both Cherryheads and Northerns do this - Cherryheads get the orange, while the Northerns get the green.........

Not every Male has it, and I don't believe I've ever seen a Colombian Male that showed it.........

 

[cdmay]

It is a random trait not related to gender. Check large groups of redfoots and you will find both males and females with 'eye rings'.
Oddly, its seems to me that individual tortoises that have more overall color often possess the eye ring.