Does AC increase carrying capacity?

Dedicated exclusively to field herping.

Moderator: Scott Waters

Post Reply
User avatar
Joseph S.
Posts: 540
Joined: June 11th, 2010, 4:21 pm

Does AC increase carrying capacity?

Post by Joseph S. » February 5th, 2015, 1:22 pm

(perhaps by increasing the range of options for thermoregulation and providing habitat for prey)


Or just make herps easier to find? What do you think? Any research in this regard?

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

Re: Does AC increase carrying capacity?

Post by Bryan Hamilton » February 5th, 2015, 1:37 pm

This topic has been enthusiastically debated in the past. You might find some of the older posts with a search.

There does not seem to be evidence that artificial cover (AC) increases carrying capacity or abundance. There is evidence that AC increases detectibility. As I remember there was a lot of discussion of ways to design a study to test your hypothesis. And some discussion of the mechanisms, such as increased reproductive success due to more opportunities to thermoregulate, that could allow AC to increase carrying capacity. Its a fun topic, I'll be curious to see how this plays out.

User avatar
chris_mcmartin
Posts: 2427
Joined: June 8th, 2010, 11:13 pm
Location: Greater Houston TX Area
Contact:

Re: Does AC increase carrying capacity?

Post by chris_mcmartin » February 5th, 2015, 3:06 pm

The study would have to be very meticulously designed...not sure how well you could set up a "control" given that two separate study areas, even contiguous, may appear identical to us, but have subsurface variation, vegetative variation, pretty variation, or other intangible differences that may give one plot an advantage over another. Artificial plots, where you literally build them from the ground up and merely provide AC in one but not the other, might be better, but even then I think the results would be merely suggestive, not definitive.

I think it'd still be fun to carry out. :thumb:

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

Re: Does AC increase carrying capacity?

Post by Bryan Hamilton » February 5th, 2015, 3:42 pm

chris_mcmartin wrote:The study would have to be very meticulously designed...not sure how well you could set up a "control" given that two separate study areas, even contiguous, may appear identical to us, but have subsurface variation, vegetative variation, pretty variation, or other intangible differences that may give one plot an advantage over another.
For sure. I'm thinking of using some proxies of vital rates such as reproductive rate, survival, or offspring size. You could then do a sort of matched case control of snakes with access to AC versus snakes without access. In thinking about it, snakes might not be the way to go. It might be better to start with something small and super abundant like skinks in midwest.

You're absolutely right about the complexity. With these types of studies, even with a lifetime, the results can still be inconclusive. I would expect the results to vary spatially even if you could get definitive data.

User avatar
Carl Brune
Posts: 487
Joined: June 7th, 2010, 10:22 am
Location: Athens, OH
Contact:

Re: Does AC increase carrying capacity?

Post by Carl Brune » February 5th, 2015, 5:53 pm

The PA Fish & Boat Commision seems to think so:

http://armgroup.net/wp-content/uploads/ ... -05-10.pdf

I'm inclined to think that habitat can be enhanced for snakes via the hand of man, including by providing various forms of AC. This would be for some species, in some situations. As others have noted, it is hard to prove. Also it would need to be done on a large scale to be very meaningful in the big picture.

Coluber Constrictor
Posts: 1162
Joined: June 7th, 2010, 6:25 am
Location: Mobile, AL

Re: Does AC increase carrying capacity?

Post by Coluber Constrictor » February 5th, 2015, 6:07 pm

I would think it generally doesn't, but I have to wonder sometimes about small snakes such as Storeria dekayi in urban settings. Not as many stumpholes and natural cover for them here.

User avatar
walk-about
Posts: 567
Joined: June 14th, 2010, 11:04 am
Location: 'God's Country' aka western KY
Contact:

Re: Does AC increase carrying capacity?

Post by walk-about » February 5th, 2015, 6:12 pm

Question for the OP Joseph...were you referencing specifically 'snakes', or all 'herps' collectively?? Deductive reasoning tells me that for certain species of herps - that AC could only enhance their numbers.

Rock ON!

Dave

User avatar
chris_mcmartin
Posts: 2427
Joined: June 8th, 2010, 11:13 pm
Location: Greater Houston TX Area
Contact:

Re: Does AC increase carrying capacity?

Post by chris_mcmartin » February 5th, 2015, 6:39 pm

I just caught a mistake in my first reply--"pretty variation" should read "prey variation," but maybe "pretty" could be a qualitative assessment as well! :lol:

Jimi
Posts: 1880
Joined: December 3rd, 2010, 12:06 pm

Re: Does AC increase carrying capacity?

Post by Jimi » February 6th, 2015, 6:04 pm

I think it would be a matter of scales, of the "AC" objects themselves, of their number and size and arrangement, of time, and also a matter of limiting factors.

If you haven't, take a look at the link from PA than Carl posted. Thanks Carl! (Joseph, maybe that isn't what you meant by "AC". Maybe you were thinking boardlines or something.) Note the assessment of limiting factors for timber rattlers, and how the state biologists developed recommendations for oil and gas operators to augment those limiting factors to mitigate for their development impacts. There were 2 principal factors - hibernacula and maternal thermoregulation. They focused on the latter. There was also the issue of incidental mortality, which was also addressed (mainly by suggesting operators gate & lock roads - probably something they want to do anyway).

They went all-in for thermoregulation. There was some great info there. This info would translate to a lot of situations, particularly other mid-to-high-latitude and/or -elevation situations. Particularly in forested areas and hilly country.

I actually think the authors soft-sold the possibility of creating den sites. There are lots of "accidental" man-made hibernacula around the country and the world. Stone walls, foundations, concrete slabs, rock-lined wells and cisterns, dumped piles of rock, concrete, or other hefty, durable garbage. Some of these are ancient, like Roman or whatever, but I've seen some retaining walls harboring sizable winter aggregations, which couldn't be more than 10 years old.

It's true people have not completely figured out how to make an artificial den for every single situation (but there are also some that work). Some of the accidental dens (just like the purpose-made ones, and the natural ones) might be population sinks in certain bad years (super-cold or super-wet ones?). But I would argue that anything that is a demographically-significant killer could never build up a big enough user group to do very much damage to a regional population. Not with the site fidelity the animals have - the "straying rate" (how many peel off to use a new den) every year is pretty low (but not zero, which is how all those old foundations and wells get user groups in the first place). Anyway that's why I mention time scales - straying rates and fecundity are going to regulate how fast carrying capacity could be influenced by even the best AC. Some places, some critters it's faster. Others, like PA horridus probably, it's slower.

Anyway, not trying to hijack a thread, but maybe prompt some exploration and contemplation, maybe some action. Lots of people here want to do something for herps, not just take pictures or bag them. Lots of guys own a little piece of ground somewhere in the woods, or dream of it. And some people are lucky enough to have herps in their yards.

I built a series of retaining walls ("urbanite", with cobble & gravel behind - looks a lot like this http://www.drought-smart-plants.com/rec ... z3R1Ip43fz) into the hill above my back-yard creek in summer 2012, I've already seen several garter snakes (vagrans) checking it out in the fall. Before the wall I didn't even know I had garter snakes. My neighbor's free-range cats are probably the biggest local limiting factor...so even if I didn't make a den (bet I have though) I've made some great escape cover. If a few trees would die - heh heh - there'd be basking opportunities too.

My neighborhood is 70 years old, these are suburban snakes, they could use a hand. 30 yards of concrete rubble (my previous crappy driveway) at the bottom of a steep hill aren't going anywhere. I bet a lot of the Northeast and Midwest guys could do this sort of thing.

cheers
Jimi

User avatar
BillMcGighan
Posts: 2308
Joined: June 7th, 2010, 8:23 am
Location: Unicoi, TN

Re: Does AC increase carrying capacity?

Post by BillMcGighan » February 7th, 2015, 12:29 pm

Anecdote only - take from it what you'd like.

On my wooded property there is much first and second growth forest, with some climax trees.
When trees fall, they are cut to fall flat on the ground, so the land is littered with logs.

Eastern Red-backed Salamanders (Plethodon cinereus) are common in the area, but searching for them on this 1 1/2 acre plot rarely turns any up; rolling logs, rocks, bark, etc. A two hour search may yield 1, and only in the cool months of October through April.
This is about the southernmost range of P. cinereus.

In 2009 I put out a salamander board line of 5 or 6 piles of grooved plywood. Starting in 2010, these board piles consistently yield 1 to 5 Eastern Red-backs per board pile per check, checking them about once a week, from Oct to April, when temps are above 45F.

If this was an impact study, it would be hard to conclude that the salamander board line caused spontaneous generation!

stlouisdude
Posts: 412
Joined: June 7th, 2010, 7:30 pm
Location: St Louis, MO / Hartford, CT

Re: Does AC increase carrying capacity?

Post by stlouisdude » February 7th, 2015, 1:31 pm

To think that the accessibility of microhabitats and shelter does not impact herps seems foolish to me. Haven't you ever walked up to a bluff and just knew it was going to be loaded with snakes? The ability to warm themselves while staying largely concealed, the ability to retreat to cooler areas, and so on make bluffs or and crevices along rock cuts a herp magnet. Well, in the fields where I put out AC it provides a similar function of shelter, warmth, and they retreat down into holes under the AC when it becomes needed to cool down. AC also attracts a lot of voles under it. Similarly, when I've shined bluffs at night it's not uncommon to see rodents (mostly mice) there either but those rock cuts and crevices still do not have anywhere near the amount of rodents that can be found under AC. I often find entire families of voles under there and sometimes I've seen them even stay under there with a snake sitting right next to them. I suppose it was not hungry! I guess my thought would be how much AC would be needed to recreate the kind of effect an extensive series of bluffs has though. I can't say if it actually creates more snakes, but it certainly makes them easier to find and I do believe it benefits the individual snakes able to use it consistently (and I've found some do).

User avatar
BillMcGighan
Posts: 2308
Joined: June 7th, 2010, 8:23 am
Location: Unicoi, TN

Re: Does AC increase carrying capacity?

Post by BillMcGighan » February 7th, 2015, 2:09 pm

I can't say if it actually creates more snakes, but it certainly makes them easier to find
Isn't that the whole issue? Is a population study accurate on just what we find?
No one with experience would argue AC doesn't increase finds.

Suppose you walk through a nice field, almost anywhere in temperate climate; maybe a creek or pond. There are untold mole, vole, gopher, mouse, shrew passages under the roots. In these passages are pits, kings, corns, milks, etc. The habitat reaches equilibrium.

How many snakes do you find just searching the field, contrasted to the same place with a well placed board line? Rock strewn slopes and ledges give us a window into their world where we can access them. Without a full impact study where a square hectare or so is dismantled, even up in trees and under the earth, and then cataloged, it's pretty hard to really know the population density.

User avatar
Tim Borski
Posts: 1855
Joined: June 7th, 2010, 6:28 am
Location: FL Keys
Contact:

Re: Does AC increase carrying capacity?

Post by Tim Borski » February 8th, 2015, 5:31 pm

I looked into this a couple or three years ago when I was chasing (mostly snakes) very hard. I found just as many snakes on the crawl after dark in good habitat with no AC or visible NC as I did flipping during daylight during good conditions. In my opinion I think they are there when the hab/forage is present, it just makes them harder to find during daylight.

Tim

Richard F. Hoyer
Posts: 586
Joined: June 7th, 2010, 12:14 pm

Re: Does AC increase carrying capacity?

Post by Richard F. Hoyer » February 8th, 2015, 10:49 pm

I haven't read through this thread so my thoughts may be a repeat of what has already been mentioned. My apologies if that is the case.

As perhaps some likely are aware (Jimi for certain), species and habitat are inseparable. Consequently, a correlation has to occur between the quality of habitat and the abundance / densities of species.

On any given tract of habitat, species numbers will decline if the quality of the habitat is degraded in a significant manner. And the reverse is just as true, that a significant increase in the habitat quality will have a positive affect on numerical abundance / densities.

So with respect to Joseph's inquiry "Does AC increase carrying capacity?" the question then becomes, for any given species, does the amount and type of A/C increase or decrease habitat quality or have no affect one way or the other?

It would be my view that certain types and amounts of A/C can improve habitat quality for some organisms.

Richard F. Hoyer

User avatar
Stohlgren
Posts: 603
Joined: November 6th, 2010, 9:59 am
Location: Athens, GA (Columbia, MO)

Re: Does AC increase carrying capacity?

Post by Stohlgren » February 9th, 2015, 6:23 am

The possibility of AC increasing herp populations would, of course, vary considerably depending on the species/location and how AC influences some of the variables already mentioned (prey, thermoregulation).
chris_mcmartin wrote:The study would have to be very meticulously designed...not sure how well you could set up a "control" given that two separate study areas, even contiguous, may appear identical to us, but have subsurface variation, vegetative variation, pretty variation, or other intangible differences that may give one plot an advantage over another. Artificial plots, where you literally build them from the ground up and merely provide AC in one but not the other, might be better, but even then I think the results would be merely suggestive, not definitive.

I think it'd still be fun to carry out. :thumb:
Dealing with variation in study areas is nothing new to ecological studies and would be dealt with by using an appropriate study design such as a randomized complete block. You couldn't get away with just one plot of each.

You would have to use the same sampling methodology for your AC and nonAC plots (i.e. you couldn't actually flip the cover to determine how many animals are there). Traps (box traps, funnel, pitfall, etc) would likely be the way to go. Another issue would be getting enough captures/recaptures to make population estimates with reasonable enough confidence intervals to be able to show a significant difference. This would probably be easier with salamanders or lizards than it would be with snakes.

Post Reply