School Me on Size Sets

Dedicated exclusively to field herping.

Moderator: Scott Waters

Post Reply
Posts: 443
Joined: September 22nd, 2012, 5:13 pm

School Me on Size Sets

Post by MCHerper » May 9th, 2016, 5:30 am

I (wrongly) believed that snakes that engaged in combat behavior had males larger than the females in comparative size, and vice versa for snakes that did not engage in this behavior. I recently read (multiple sources) that the female copperhead (A. contortrix) was larger than the male. I understand that the copperhead does engage in this combat behavior. Is the copperhead a single outlier in this rule, or was I altogether wrong? Is there a single factor or factors that determine relative size of male vs. female (besides females being larger to carry eggs/developing young)? Please tell all! Thank you!

User avatar
Posts: 121
Joined: August 10th, 2010, 10:25 am
Location: southwest US - NM

Re: School Me on Size Sets

Post by nhherp » May 9th, 2016, 7:21 am

Male reticulated pythons are smaller than females and will also combat , to severe injury and/or death, with other males. I once had to put over 100 stitches, combined with glue, into a friends male retic. He had taken the word of a prior owner who gave him a "female" which he failed to sex for confirmation after obtaining it. Somewhere I have a series of photos of the carnage the poor animal endured. It recovered and lived healthy for many years afterward.

Its intriguing that retics raise the bar so heavily when compared to the toppling/dominance type methods of venomous pit vipers.
Morelia ssp (scrubs, carpets..) are also known for male combat and have smaller males then females.


User avatar
Bryan Hamilton
Posts: 1217
Joined: June 10th, 2010, 8:49 pm

Re: School Me on Size Sets

Post by Bryan Hamilton » May 9th, 2016, 8:54 am

I wasn't aware that female copperheads were larger than males. There are some odd behaviour in that species involving males. Chapter 5 of Snake Ecology and Behavior has a section on copperheads and gives a good overall paradigm for mating systems. Male combat is only a piece of the puzzle.

I've heard that female sidewinders are the larger sex. I assume male combat exists in that species.

I think the larger male size leading to male-male combat is more of a generalization. For the most part, it seems to hold up, but I'm not surprised there are exceptions. Probably lots of exceptions.

Posts: 1874
Joined: December 3rd, 2010, 12:06 pm

Re: School Me on Size Sets

Post by Jimi » May 9th, 2016, 9:15 am

N - I think you were generally right in the first place, and you have recently been led astray, or confused by the exceptions. You were certainly not altogether wrong. Life history and mating-systems theory both have plenty to say on this subject. But never forget - all that material was made up by humans to explain and predict what we see in the real world - the one outside our heads. The real world is considerably more nuanced and interesting.

Yes, male copperheads are vigorous combatants. Also, on copperheads specifically - my recollection of the few really big ones I've found is that those were all males. But surely someone has published a methodical examination of many of the thousands of museum specimens, or the results of a long-term field study (trapping or something) that presents some "big data", not "data-point" anecdotes. My intuition is that males are bigger, and the internet has gone and screwed things up with unvetted info.

I don't have it on the bookshelf I'm looking at right now, but I recommend to you Gloyd's Agkistrodon-complex tome. It's a beauty well worth owning. The book Bryan cites (edited by Mullin & Seigel) is also excellent.

Bryan - yes, sidewinder is one of the rare rattlesnakes with bigger females than males. Lanceheads, and tree vipers (both Crotaline and Viperine), routinely have bigger females than males (occasionally to an extreme, e.g. in Tropidolaemus), otherwise in the viper world generally, males are bigger. In some cases, much bigger. That's what I have seen (wild & captive) and read, anyway.

Posts: 625
Joined: June 7th, 2010, 5:02 am
Location: Southern Cal.

Re: School Me on Size Sets

Post by craigb » May 10th, 2016, 11:21 am

Many pit vipers have male combat behaviors....

Asian Herpetological Research 2015, 6(3): 237–239
DOI: 10.16373/j.cnki.ahr.140040
Male-male combat behavior occurs in over 120 snake
species from four families (Boidae, Colubridae, Elapidae
and Viperidae; Shine, 1994). Reproductive success
presumably depends on the males’ combat ability because
they are competing for access to females; this correlation
is has been understudied in tropical snake species.
Although ritualized male combat is well-documented in
pit viper species where males reach larger body sizes than
females, combat has rarely been reported for species in
which the female is generally larger (Shine, 1994), as is
the case with C. rhodostoma (Malayan Pit Viper).
Calloselasma rhodostoma is endemic to Southeast
Asia and is one of the few pit vipers that exhibit femalebiased
sexual size dimorphism (Chanhome et al., 2011).
In Sakaerat, C. rhodostoma exhibit nest attendance and
defend their clutch by coiling around the eggs through
gestation (Hill et al., 2006). The distribution of C.
rhodostoma includes much of Indochina (Thailand,
Malaysia, Lao, Cambodia, Vietnam, Singapore) and
Indonesia (Chanhome et al., 2011), and is the species
First Record of Male Combat in a Wild Malayan Pit Viper
(Calloselasma rhodostoma)
Colin T. STRINE1, Curt BARNES1, Inês SILVA2, Bartosz NADOLSKI1, Taksin
ARTCHAWAKOM2, Jacques G. HILL3 and Pongthep SUWANWAREE1*

This full paper is a short but interesting read. It has some excellent pictures of observations.

Posts: 1874
Joined: December 3rd, 2010, 12:06 pm

Re: School Me on Size Sets

Post by Jimi » May 11th, 2016, 9:21 am

Great contribution Craig, thanks very much.

The SE Asian crotalines (where the subfamily originated...) are unique in that relatively (compared to those of NE, C, & SW Asia, plus the Americas) many are oviparous and of those, I believe most have maternal nest-attendance. In those cases - like Callosellasma - it is more typical for the female to be larger.

I'm not sure about the ubiquity of male combat in the maternal nest-defenders. For any given taxon, do they only exhibit one or the other behavior, or do many taxa have both? When both behaviors exist, which behavior typically "wins out" in terms of gender size? With Callosellasma - showing both behaviors - obviously it's maternal nest defense that "wins" in terms of gender size - bigger females & better hatching success would seem to be more adaptive, as males are "just sperm donors". A follow-on question - have male combat & male "gigantism" been facilitated or driven by the advent of viviparity? Natricines would suggest not, but...who knows about the other groups?

My God I love vipers, ha ha very interesting.

Posts: 8025
Joined: June 8th, 2010, 7:12 am
Location: Hesperia, California.

Re: School Me on Size Sets

Post by hellihooks » May 11th, 2016, 6:47 pm

when i was married, and asked 'who wore the pants in the family?"... i said " we both do... hers are just bigger." now i gotta pay for slaps that hard... :crazyeyes: :lol: :lol: :lol:

Posts: 443
Joined: September 22nd, 2012, 5:13 pm

Re: School Me on Size Sets

Post by MCHerper » May 24th, 2016, 5:30 am

Thanks for the info!!

Post Reply