# Help catching gravid snakes



## naivepom (Jan 9, 2010)

This call for help goes out to anyone herping in the Townsville/NQ area...

I am currently conducting a study on the effects of climate change on snakes. I need gravid snakes for this study so I can subject the eggs to different temperature treatments to see how long/strong/quick etc the babies turn out. If anyone regularly goes out herping in the Townsville/Girringun/Tully/Wallaman regions and comes across gravid snakes reasonably regularly then please get in touch. I have relevant permits and really need help to catch a sufficient number of specimens. Any species is considered though I would very much prefer it not to be anything too lethal and it has to be oviparous.

Please PM me if interested, this is sensitive scientific work and first and foremost have the welfare of the snakes in mind so references/prior experience essential. Thanks.


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## garycahill (Jan 9, 2010)

Wouldn't this experiment be detrimental to the snakes though?
By subjecting them to different temps, some will not hatch. 
This will put more strain on a species that is already in decline.
Also, what authorisation do you have from parks & wildlife or relevant government body to do this? 
As all wild snakes are protected by law, killing of eggs/embryos would also be covered.


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## Serpentes (Jan 9, 2010)

This is a bit strange, why don't you have your experimental protocol (species and sample sizes) determined prior to approaching volunteers? It sounds like you're setting yourself up for some statistical nightmares (i.e., N=1 or 2). I'm also surprised you got animal experiment ethics approval without a rigid predetermined experimental protocol. It is also the wrong time of year to be scouting for gravid snakes of most species. All of my research on sex determination goes into swing collecting females in August through November.


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## naivepom (Jan 10, 2010)

garycahill said:


> Wouldn't this experiment be detrimental to the snakes though?
> By subjecting them to different temps, some will not hatch.
> This will put more strain on a species that is already in decline.
> Also, what authorisation do you have from parks & wildlife or relevant government body to do this?
> As all wild snakes are protected by law, killing of eggs/embryos would also be covered.



I am hopefull it will not be remotely detrimental to the snakes. They will be kept in laboratory conditions with day/night lighting and temperature cycles, hides and ample water and food. In fact, they will be almost certinaly be better off in temporary captivity. All snakes (babies and adults) will be returned to point of capture after the study. With regards the babies, the temperature changes I am subjecting them too are very narrow (to approximate future climate) and it is in my best interests to not have them in temperatures where they will not hatch. I am modelling conditions expected in 100 years - if the eggs go bad from these temperatures then it is a superb indication that this species needs urgent help (and the death of a few in captivity will be meaningless as without the study the species would be extinct in the wild anyway). Furthermore, the eggs will be kept safe, warm and in correctly watered vermiculite - conditions specifially designed to approximate wild conditions - with one difference, there is no chance of predation in the lab or disease/fungus contamination (as all eggs are kept separate) so in fact it is, at the very least, not detrimental to the species. Also, I need graivd females so it is highly unlikely i will be finding gravid females of extremely rare species as they are extremely rare to find. I find approximately 40 keelbacks a night at the moment and of them about 0.5 are gravid so what are the chances of finding a suitable numner of gravid rarer snakes?

I have all suitable permission and permits (ethics, parks and holding) but as I say will need to know the particulars of any volunteer intimately before I trust them to help responsibly with the study.


To answer the other poster, yes exactly, I will have huge problems with n numbers - hence the request on this forum. I know how many I would ideally like of each species to make a powerful statistical test and have been out every night for the last few months to collect these numbers but time is limited and I have found the only way I will collect enough is to enlist other help - and what better place to do it than on a forum of people who actually know where to find snakes, what the snakes are and whether they are gravid. I could easily enrol the help of a bunch of enthusiastic uni kids but I would prefer experience. And also agreed, now is not the best time for gravid snakes but funding money doesnt time itself to coincide with snakes laying eggs so I have to do the best with what I have been given. Hope this addresses your concerns.


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## eipper (Jan 10, 2010)

Naivepom,

Not try to poke holes in your study but.....

There are plenty of spots in the wild that exceed CT Max for many species, the snakes just thermoregulate and move to a cooler Microhabitiat....these will still be available for the wild snakes, so therfore you should not see a decline due to fairly small temperature rise regardless around Townsville. Ovipostion in wild snakes is not well known, more so the selection of oviposition locations? (What does the female look for before depositing eggs? are there chemosensorary cues, temperature, humidity are they able to know if an area is subject to periodic flooding etc?) Without knowing why a gravid snake chooses to lay her eggs in a particular location, you cannot represent this in a lab enviroment....you would at the very least need temperatures of wild nest sites and then start from there.

I have no doubt that climate change may pose a threat to some species, how the species it is/will threaten will more likey be Montane species... (Eulamprus lutrelateralis from Eungella comes to mind) that are already isolated from the lowlands of apparently suitable habitat.....if that area warms up that may be very serious. There are no endemic snakes around Townsville so you are already dealing with species that are reasonably wide ranging.

For Something closer to home you could look at Cophixalus mcdonaldii from Mt Elliott. (Another montane species close to T/Ville) that may certainly be affected by climate change

Cheers,
Scott


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## naivepom (Jan 10, 2010)

eipper said:


> Naivepom,
> 
> Not try to poke holes in your study but.....
> 
> ...



I quite agree Scott, there are a huge number of little understood factors involved and, of course, snakes can choose a different microclimate to offset effects of climate change. 

Also, I quite agree, it is very likely that montane/restricted distribution reptiles are likely to be most at risk. 

HOWEVER, this is the point of scientific study, we know very little about a lot of these factors so we conduct studies that helps improve knowledge. I am not claiming this study is perfect but it is still valid. Hopefully further studies will emerge that look more at a different aspect of reproduction and then knowledge can be combined and so on... I do not know where many snake species oviposit but the majority of published papers find that eggs are mostly laid in burrows/soil cracks etc and not out in the open. To this end I have planted a number of temperature sensors at varying depths in the ground in various locations and they all show an amazingly stable, constant temperature and this provides the basis for the 'control' temperature treatment. 

Furthermore, several recent papers have shown that many reptiles are already living close to extremes of temperature and a few degree rise in temps will be critical. This applies to more than just montane species. It may be that in the current situation there are very few suitable microclimates left available and that small increases in temperatures will be critical. We just dont know, and this is what I am trying (in some small part) to address. Many thanks for the comments though, it is all gratefully received and helps keep me thinking along the right tracks. I started the thread to ask for practical help in the field rather than the theoretical and statistical framework but its all good 

Oh and one final point about snakes not being affected by a small change in temperatures - it isnt necessarily about snakes being happy to live in 31 degrees whereas previously it was 28 degrees - it can often more be extreme weather events that are associated with climate change such as the number of consecutive days above CTmax. Animals such as possums currently can survive several days above a certain temperature but if this heat wave persists for more than a few days (as is expected under future climate change scenarios) then it rapidly becomes fatal. Key thing is, there is a huge amount we dont know, hence this study (and hundreds similar).


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## waruikazi (Jan 10, 2010)

I've caught a few gravid snakes in the past. Several of these snakes have gone on to lay a few days after capture while in my care. Alot of the cluthces that have been layed have ended up dieing and i think (and it is only conjecture on my part) that the stress of capture can cause them to lay prematurely causing the eggs to die. 

Although i think your study will be intersting i recon you would have an easier time if you take WC snakes and breed them in your lab.


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## jinjajoe (Jan 10, 2010)

Stress would surely cloud the chances of any conclusive results ??


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## naivepom (Jan 10, 2010)

Stress is a concern but you can do things to mitigate this (quiet room, no through-flow, plenty of hides/water and day night light cycles). The temperature treatments are being imposed on the eggs not the adults so up until they lay they are provided with a temperature gradient. Stress is undoubtedly there but is present in the same proportion for all the animals so it doesnt affect the comparison. 

Breeding wild snakes is not an option as it is too time consuming for my deadlines and there is very little knowledge on even how to breed something as common as a keelback.


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## waruikazi (Jan 10, 2010)

naivepom said:


> Stress is a concern but you can do things to mitigate this (quiet room, no through-flow, plenty of hides/water and day night light cycles). The temperature treatments are being imposed on the eggs not the adults so up until they lay they are provided with a temperature gradient. Stress is undoubtedly there but is present in the same proportion for all the animals so it doesnt affect the comparison.
> 
> Breeding wild snakes is not an option as it is too time consuming for my deadlines and there is very little knowledge on even how to breed something as common as a keelback.



The knowledge is there if you look for it, I have mate who has bred keelbacks. 

I'm not knocking what you are doing but i do think the way you are doing this isn't going to work real well for you. If breeding them yourself is going to take you too long then perhaps you could look at purchasing gravid animals or eggs of your desired species.


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## Serpentes (Jan 10, 2010)

Rick and Greg have already researched keelback reproductive ecology, quite well.

One thing, you seem to have the assumption that the thermal ecology of snakes is static, whereas it is labile due to behavioural thermoregulation and microhabitat selection (as pointed out by Scott, above). Nonetheless, inference from incubation-induced changes in fitness will be an interesting story, if you can meaningfully assert fitness from hatchling performance breadth variance. Make sure you have a lot of incubators available for split-clutch designs, and that the eggs are incubated in separate containers,, or the experiment becomes confounded. You will have to decide on the allocation of eggs to treatments and how you will compensate for maternal affects. There is a mass of information available on this. All of your statistical designs should be constructed prior to data collection, or things can be more challenging than they need be.

There is also the problem of phylogeny, so make sure you choose your species wisely if you want to compare them. Yo will also need to show that the present distribution of snake species is determined by incubation requirements- at the very least correlate incubation temperatures with geographic range. Otherwise you have no story to tell: if geographic range is not governed by incubation requirements then hatching fitness at different temperatures tells us very little about the influence of climate change on distribution. A simple bioclimatic model would be more informative. 

Finally, look into some of the work done on tuatara reproduction and climate change, it may help.


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## naivepom (Jan 10, 2010)

There is lots of knowledge out there agreed but unfortunately I probably dont know your mate  though it would certainly be useful to hear from him about it if you have his contact details?

Yes it isnt what I would have in my mind as a 'perfect' experiment but as I mentioned you have to make do with the time/financial etc constraints you have - all science is governed by this (in fact if you see some of the stuff that gets published and see how it was conducted it makes this study look like a rigorous, polished proof!). I do not have time to breed and I do not have the money to pay for eggs (and need it to be from WC specimens so as not to add a further confounding factor) so the imperfect way I mentioned is the only one I can think of (though open to suggestions) so I have to make do, and hope others can help.


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## naivepom (Jan 10, 2010)

Many thanks for your comments Serpentes. Yes snakes use behavioural thermoregulation and microclimate selection but temperatures underground are amazingly consistent across habitats (even burrows under rocks compared to those in open ground or in tree root systems) so maybe they do not have as much flexibility as we think. Just a possiblity though.

Yes the design is certainly a headache. All eggs are separately incubated and randomly allocated to a treatment. The mothers are tested on all the same tests as the neonates to hopefully give an idea of inhereted characteristics e.g. if one mother is an excellent swimmer and all her offspring are also way better swimmers than other offspring, irrespective of temperature treatment, then this can be provisioned for.


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## Sdaji (Jan 10, 2010)

This probably would have been better done on captive snakes, there is already at least one lab in Australia producing hundreds of snake eggs as a by product of their research, and several others producing large number of lizard eggs.

Keelbacks are very easy to breed, a friend of mine got five clutches out of one in one season. All you need is to keep them at the right temperature, feed them lots of fish, give them something to swim in, some land, and a nesting box if you want to get fancy.

Anyway, if for your own reasons you want to/have to use wild snakes, Keelbacks sound like an excellent choice to go with. On my best night in Townsville I saw over 100 Keelbacks in one night, so I don't doubt you're able to fairly reliably go out and find at least 40. If about half the females are gravid, surely you wouldn't need many good nights to get more gravid snakes than you require, or are you after multiple species? If so, your sample sizes are probably going to be too low to be useful. You're going to get much better results from 100 eggs from a range of females from one species than one clutch from each of 20 species.

Scott made some very valid points about the fact that you're going to be working with non endemics, which have continuous gene flow between your area and areas which already have the future climates you're looking at. As he says, they're just going to thermoregulate and choose different nesting sites to compensate. To get something meaningful, you would want to be looking at animals from a restricted range, or taking animals from an extreme of their range and looking at treatments outside the range in the direction of that extreme.

Snakes will cope just fine with unusual extreme weather events, they are excellent at finding a nice microclimate retreat. Obviously a cold snap will never hurt the snakes of Townsville in any serious way. A long heat wave is unlikely to do much either - there are plenty of cool retreats to use, you just have to go underground. I doubt a two degree temperature increase for a week or two is going to have any serious affect on the snake eggs. The worse likely scenario is the odd clutch being lost and some very mild affects on the remaining hatchlings, so at the most extreme you might have a slightly good or bad season, but that has been the case for the last few million years. Burrows/underground sites (oviposition sites) may be fairly stable if the snake wants them to be, but there is a range of options available to them which allow selection of preferred temperature (aspect, shade, ground cover, etc etc etc). Many Townsville species have massive ranges, many include areas to the north, including overseas (how many also exist in PNG?), some even include Victorian highlands!

What type of study are you doing? My honours year project looked at thermal affects, largely in the context of climate change. You probably don't, but if you want to, feel free to get in touch for a chat about your project. My study animal was a grasshopper which had very limited option of incubation sites (they had to be in the ground within about a metre of their home shrub) and the animals themselves had to spend their whole life in one small shrub, so there was little opportunity to thermoregulate, and no way to get significantly below ambient temperature. For them, a freak heat wave could easily mean local extinction, and their extremely low dispersal means that only needs to happen every few hundred/thousand years.

I'm not sure how relevant your results will be in the context of climate change to the snakes of Townsville (which naturally has a reasonably extreme and variable thermal climate anyway, which probably explains the lack of endemics, meaning you're working with more generalised species), but you should come up with some interesting data which will be of some use in some context. It's a bit late in the season, as others said, so good luck getting it all happening in time, and good luck with all your results  Please let us know when you're finished, I would love to see the results, and am sure you will come up with data which is very interesting and useful.


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## naivepom (Jan 10, 2010)

Sorry a few more things re-reading your post Serpentes.

I have read quite a few of Rick and Greg's papers, including one on the reproduction of keelbacks and one where they effectively do this same experiment but looking at constant versus fluctuating incubation temperatures. However even in the paper specifically about reproduction in keelbacks it doesnt even mention what mating system they use, just the possible length of the season.

And you have also raised a serious issue about proving current snake distributions are limited by incubation temperatures in order to show climate change will have an impact. I'm not sure I quite understand this - could it not be that they currently are limited by any number of other factors but in the future, may be limited by climate? I hope I'm not missing something here but I dont see why they need to currently be limited by climate.


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## naivepom (Jan 10, 2010)

Many thanks Sdaji sending PM now....


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## Serpentes (Jan 10, 2010)

The Townsville region is home to several endemic species reptiles (no snakes come to mind though), but these are due to quirks of biogeography rather than climatic generalities. For example, the skink Lampropholis mirabilis has a very tiny distribution around Townsville, and it has evolved to suit the conditions of its present distribution (which may or may not have been much larger in previous climatic events). Nonetheless, Lampropholis mirabilis has a thermal ecology that would allow it to inhabit a massive geographic range, yet it's microhabitat requirements are such that it is stuck in little isolates, surrounded by conditions which are inimical to it's fitness and range expansion. Other wet tropics endemics with tiny ranges also seem to have a performance breadth which, while evolutionarily static, simply doesn't account for the narrow geographic distribution (such as Lampropholis robertsi and L. coggeri). 

What would be informative is to compare different eco-types of carpet pythons to determine their range of incubation tolerances against those imposed by different thermal habitats (rainforest and woodland, for example).

I used to think that thermal biology was a simple measurement alluding to reproductive success, sadly the more I learn about it the less I know about it. One thing I will tell you is that maximal performance alone does not allude to geographic distribution, if fact it appears to be an inverse relationship, until you look at responses other than performance maxima.


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## naivepom (Jan 10, 2010)

Serpentes said:


> What would be informative is to compare different eco-types of carpet pythons to determine their range of incubation tolerances against those imposed by different thermal habitats (rainforest and woodland, for example).



This was very much a possible consideration. We were actually going to look at closely related snakes such as childrens vs spotted and compare their habitats and incubation tolerances.

With regards to performance maxima I see your point that it doesnt necessarily translate to distribution/success. I am looking at morphological, behavioural and physiological characteristics and including both maximum speeds and endurance type tests so hopefully I can infer that some are better equipped to succeed whereas others are more at risk.

Also to answer the previous poster - yes keelbacks are my main focus as I would rather have 100 of one species than 5 of another. Considering they are supposed to have year-round breeding (or at the least an extended breeding season) only a TINY proportion of the 40 snakes I see a night are gravid (half are males, the other half are juvenile so that already puts it down to only 10 possibles from the original 40).


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## Serpentes (Jan 10, 2010)

Sorry NativePom, just read you post above. If geographic range is not presently correlated with climatic conditions then there is no reason that it will become so following climate changes. Climatic range is a very hard thing to quantify, because it is so variable with altitude, aspect and habitat type, plus more. Let look at two closely related taxa- diamond and carpet pythons. Taking a population of diamond pythons from Sydney vs. carpets from Darwin: you would expect the former to have a lower incubation requirement, and be more tolerant of variability in incubation temperatures both within and between clutches. This is a logical assumption given the different climatic zones. However, you can incubate both species in the same incubator, at the same thermal regime and they will pop out. What you want to look at is the variability of hatchling phenotypes, as more variation will be evident in a species that has a broader climatic distribution. You may find that between these two species, the diamond python shows the most resilience to both hot and cold temperatures throughout incubation, and appears to be capable of withstanding very warm climatic regimes, perhaps warmer than those tolerated by the carpets from Darwin. The fitness costs however, may be driven by some aspect of adult ecology, such as an inability to withstand prolonged periods of cold in the carpet python, or an inability to metabolically compensate (inverse acclimation) during hot and dry conditions. 

From the above example, you can see that there is little evidence showing that the incubation requirements drive distribution. In fact, if you look at incubation tolerance over a narrow range of temperatures (27-34C) you may decide that the diamond python is the species that will reproduce in warmer conditions than carpet pythons. Mapping the temperatures tolerated by incubation of each species would show a potential for diamond pythons to usurp the range of carpet pythons, yet this doesn't happen! Thermal ecology is a complex phenomenon, so just be open to accepting your null hypothesis. Again, my big hint is to look into the variance within and between clutches.

Sorry I could go on about this all day. My research for the past 6 years has been on the effect of climate on distribution. I should be writing it down in a manuscript rather than the internet 

P.s. now that you're giving out more info on your plans I can better understand your position. Are you working with LS?


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## naivepom (Jan 10, 2010)

Yes Serpentes I am working with LS - should I know you!?

And I am EXTREMELY open to the idea of accepting my null hypothesis!

I take your point about the diamond pythons, though could effects be a little more subtle than this? Yes both pythons may pop out if incubated at the same temperature but the offspring of the diamond may be weaker/thinner/malformed etc etc (or may not be) so not necessarily direct hatchability. I guess this is why you mention hatchling phenotype variation. I am looking at as many traits as I can think of (pigmentation, anti-pred, swim speed/endurance, thermoreg preferences). In theory if any one of these is sensitive to incubation treatment then it has the potential to effect species fitness. Of course if these affected traits compensate over time then the whole argument is largely void!

In all honesty, even if I can reject the null hypothesis, the scope of the project wasnt going to be so large as to start inferring where future distributions of snakes may be, just about the potential effects that may occur, the effect of climate on distribution is WAY too complex for me. And agreed about writing this down in a manuscript rather than internet, the same thought had crossed my mind. At least this helps prepare me for the defense of my seminar!


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## Serpentes (Jan 10, 2010)

I only like to offer questions because that's the ultimate outcome of sending in your manuscripts or presenting seminars. I always welcome people tearing apart my work- if I have made an error in experimental design, I'd rather know about it so I can learn and proceed in a more meaningful manner. You have certainly come up with good answers about your project design, and I think that some good data will come of it! Testing several traits indicative of (or potentially linked to) performance shows that you're on the right track as far as current theory goes. I have relied on Angilletta et al (2002). The evolution of thermal physiology in ectotherms. J Therm Biol 27:249-268 to build a lot of my theoretical construct. If you don't have it, it's an excellent paper by a true herp freak. 

You should also be able to defend your seminar just fine. Remember that sometimes the best response to troublesome questions during a seminar is "That's an excellent question, and I would certainly like to discuss it with you more in depth after the seminar when I can spend more time to understand the points you've brought up". All the while you can be thinking "shut up you don't know what you're talking about, I want to get outta here!". .

Anyway, your supervisor and I don't get on too well, due to an error in judgement I made as a student of hers (undergrad) back in the 1990's. Well, she still wasn't smiling in my presence at the 2006 ASH meeting, so I don't think I'm forgiven yet. Uncle Alford likes me though, although he thinks I should be dead from snakebite long ago. As him about taipans and Kirrama, he'll know 

As for finding gravid snakes, I reckon that getting in touch with those on the list for snake relocations in T'ville could be fruitful. There are some good, very good, amateur herpetologists in North Queensland, and JCU is producing some great academic research too (Brett Goodman has set a benchmark)!

If you have any stuff to chat about feel free to PM me. 
-S


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