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SoCal Endangered species herping, part 4

Posted: August 28th, 2010, 5:46 pm
by Sam Sweet
Here’s a second installment on the biology of arroyo toads, Bufo californicus. The first post (viewtopic.php?f=2&t=1274) covered aspects of reproductive biology, so I’ll focus here on juvenile and adult animals.

Arroyo toads are members of the Bufo americanus species group, which is basically limited to regions with reliable summer rainfall – B. californicus in southern California is a relict of wetter conditions that ended 10-12,000 years ago, and it really should not still be present in a region where annual rainfall of 20” or less occurs only in the winter months. It has been able to persist owing to some unusual topographic features. Without getting too technical, here we have mountain ranges parallel to the coast that are being uplifted vey quickly, with deep canyons cut in wetter times. The foothill portions of these canyons are backfilled with sediment that has accumulated because current rainfall is incompetent to transport it away, and the current streams meander across this backfilled surface, as seen here:

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These sand deposits store large volumes of winter storm runoff, and meter it out long into the summer, creating sections of semipermanent stream flow in a climatic zone that should no longer have anything but ephemeral streams. All of the riparian herp species in southern California are dependent on these perched aquifers, but about ¾ of them are now submerged under reservoirs.

Within these drainages there are typically a series of old stream terraces, now drained and covered with chaparral, and low terraces bordering the current stream where groundwater is close enough to support willows and cottonwoods, and oaks at the edges, with sandy benches covering old meanders of the flood channel. Those benches get washed over on a cycle of decades, and reworked on a cycle of centuries by infrequent heavy floods.

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Arroyo toads don’t venture into chaparral, so their distribution is confined to the youngest terraces and the streambed itself, and often that’s not much. By contrast, Bufo boreas loves chaparral, and may disperse miles horizontally and thousands of feet vertically away from breeding sites. Western toads will also use a far wider range of breeding sites; in a nutshell, that’s why the one is doing OK and the other is endangered.

On average B. boreas breeds earlier in the year and metamorphoses sooner than does B. californicus, but juveniles of both species overlap from late May into early July. Young B. boreas quickly become nocturnal, but find shelter in burrows, under rocks and in dense vegetation along the stream until they reach a body length of ~20 mm, at which point they all disperse upslope. Juvenile arroyo toads dig in at night and are active by day even at very high temperatures, and they will remain as long as damp sand or gravel is available, into September in some places and years. They don’t disperse far from the streambed, but become nocturnal as the substrate goes dry.

I’m often asked to identify juvenile toads suspected of being B. californicus, and nearly always they turn out to be B. boreas. Here’s a set of each, arroyo toads first, followed by a couple of comparative photos.

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They’re really pretty different animals. Side by side notice the more distinct “neck”, pale middorsal line, uniform dorsal ground color, rounded parotid gland, and orange-red “warts” on B. boreas, vs. the short, wide head, pale V on the eyelids, light front half of the oval parotid gland, mottled dorsal ground color, and smaller, yellowish “warts" on the juvenile B. californicus.

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If you’re really clueless after all that, turn them over. Bufo californicus are always immaculate white ventrally, whereas even the tiniest metamorph B. boreas have dark speckles (that increase in density with age). Note that both have the standard pigmentless ‘diaper’ of water-absorbing skin – this is why you’ll never see a toad drink, they take up all their water through their little bottoms, even from just damp sand.

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So how about adult toads outside of the breeding season? Both species are nocturnal, and usually active from dark to about midnight. Western toads can dig in but seldom do, using mammal burrows in the open or logs and woodrat nests in the chaparral. By contrast, arroyo toads are always somewhere near the creek, and dig themselves in every night. Both species return to the creek to soak, arroyo toads about every third night, western toads maybe weekly into midsummer, but both become much less active in late summer and fall. When you encounter them out at night they are either foraging or traveling to and from the creek.

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Arroyo toads are doing things a little differently. In addition to soaking

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They are foraging, but very specifically. It is not very widely known that arroyo toads are ant specialists, but they are every bit as specific as horned lizards in this preference. What they are after are velvet tree ants, Liometopum occidentale, which make nests in large tree trunks and send out foraging columns after dark, where the ants locate and milk honeydew from aphids. Liometopum trails are in the same place every night, often for months and sometimes between years, and that’s where arroyo toads are.


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An arroyo toad seen after dark anywhere else (outside of breeding season) is either traveling to soak, or heading toward one of the ant trails it knows. Another way to show this is to pick up some feces – remember that lizard feces have a white urates cap at the upstream end, whereas toad poop doesn’t

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Bust them open, and you’ll find a wide range of insect parts in western toad turds, especially a lot of large beetles, whereas arroyo toad feces are composed almost entirely of ants.

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As always, there is more, but enough for now. Appreciate your riparian areas, they are pretty special places.

Re: SoCal Endangered species herping, part 4

Posted: August 28th, 2010, 6:24 pm
by Fundad
If you’re really clueless after all that, turn them over.
Thats pretty much me, but your lesson and post will hopefully make me a little less clueless.. :D

I had no idea the only ate Ants, IMO that makes them even more vulnerable, than just the waterway issues
we have.

Thank you so much for taking the time to post this and share this with us.. I for one appreciate it.

:beer:
Thanks Again Sam
Fundad

Re: SoCal Endangered species herping, part 4

Posted: August 28th, 2010, 6:48 pm
by FunkyRes
Any thought of turning this into a herpnation article?
I'm serious.

That info about the toad its natural history was a really neat read.

Re: SoCal Endangered species herping, part 4

Posted: August 28th, 2010, 9:32 pm
by Joseph S.
Fascinating. You mention B. boreas disperses miles from the breeding site. But how far can they be from water? It seems to suggest that some of these toads are undertaking long trips to refill their water supply(and it seems thy must do this frequently) which I find quite mind boggling.

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 7:41 am
by hellihooks
Good Stuff Sam!
I also did not know they were exclusively ant-eaters. Todd B. had been asking if Arroyo's were still present in a certain Hi-D locality, and while I haven't found any this year myself, I talked to the guy who manages the area and he says he hears them trilling every night. I have unlimited access to some 2400 acres of the west fork of the Mojave rv watershed (from Deep Creek to Flores Ranch) so if you ever want to check it out... consider it a standing invite. jim

I too am constantly amazed at some of the places I find W. toads... way up in the Mts... out in the middle of the desert... I'd be hard-pressed to think of ANY area I HAVEN"T found them... :shock:

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 7:56 am
by MHollanders
Wow, great post!

Later, Matt

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 9:26 am
by Robert Hansen
Excellent, Sam. Lots of cool stuff I didn't know, especially the bit about the ant diet and the fidelity of ants to specific trails. I would imagine that any sort of anthropogenic interference with those trails might muck things up for the toads as well.

B

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 10:44 am
by reptilist
MMmmm Mmmm Mmm... That there was some good toad larning! I thanky!

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 11:27 am
by klawnskale
Sam: What's the latest take on the relationshio genetically between Bufo (Anaxyrus) californicus and Bufo (Anaxyrus) microscaphus?
Is there enough genetic differentiation found between these species to determine they are truly distinct from each other?

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 2:04 pm
by jonathan
Awesome post again Sam. I was particularly interested in your description of the origin of the sediment deposts in SoCal canyons that allow the toads to exist in Southern California.

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 4:45 pm
by Kent VanSooy
Excellent post, particularly the biogeography. Additional knowledge about the toads is much appreciated by the SoCal NAFHA folks. Thanks Sam!

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 5:19 pm
by Fundad
Any thought of turning this into a herpnation article?
I'm serious.

That info about the toad its natural history was a really neat read.

Great idea... I like it.. :thumb:

Fundad

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 7:47 pm
by Sam Sweet
Glad to hear that stuff like this is of interest, even w/o any red snakes. Whether it would be a good HerpNation article or not probably depends on whether you want to buy something you can read here free, eh?

Other responses, in no particular order. Bufo boreas will disperse an awfully long way from any semipermanent water source that could be used as a breeding site -- if there is dew or fog drip, that can be enough to keep them going. How far, no one really knows, but adults turn up in numbers crossing the crest of the Santa Ynez range here in May-July, and again in December-January, and most are headed one way in summer, back in winter. Since there are no breeding ponds or streams on either slope for at least 2,000' vertically, I sorta wonder if they are hiking from the interior over into the coastal fog belt for the summer, then back over the ridge to breed, 3-4 miles and ~2,000' elevation change each way. You'd need relatively big radiotransmitters (long battery life) to find out, and there's no safe way to attach them to toads. Belts don't work with boreas, they are narrow-hipped and can shed any belt by simply extending both legs back and wiggling loose.

Ants are pretty good at maintaining their trails, as anyone with a kitchen knows. Velvet tree ants do need larger trees, and they'll disappear if the trees are lost to flooding, road- and trail work, or fires that get into the riparian zone. They are also vulnerable to being wiped out by Argentine ants, which have successfully colonized open streambed habitats in coastal California S of the LA basin. Whether Argentine ants can jump from suburbia to wildlands farther north or inland isn't clear yet. Arroyo toads will certainly eat other insects, but they really target tree ants when they can.

The Arizona and California populations of arroyo toads are pretty similar genetically, with about as much differentiation among drainages in California or in Arizona as between the two regions. That's no surprise, since river corridors existed across the Mojave until ca. 8-10,000 years ago. I'm not going to worry much about what we call them (californicus or microscaphus californicus), as it's not an open-and-shut case for either interpretation.

Perched aquifers in intermountain valleys leave telltale signs in the form of stepped terraces, as in the photo here (5 visible, with bits of another 2-3 detectable farther upslope in this case). The steps probably correspond to either massive flood events, or (more likely) temporary pileups of large boulders or landslides in some narrow canyon downstream. Those events flatten out the local stream gradient for a while and lead to more deposition until the chokepoint clears. It's cheap and efficient to put dams in those narrow cuts, and any map of southern California will show you plenty of examples of where there used to be arroyo toads (et cetera) upstream.

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Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 8:08 pm
by hellihooks
Would beaver ponds, supporting cottonwoods and Oaks along a desert riparian corridor, likely be suitable for arroyos, if upstream from a known population? I'm considering widening my parameters. thx.. jb

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 8:29 pm
by Sam Sweet
I've never seen arroyo toads use beaver ponds, but they easily could use the upstream ends if conditions there were right. Male toads seem to be pretty choosy about calling sites -- overall, they generally pick a place where they can face shore in 2-3" of water (that is not stagnant, explained below), with no major obstructions such as cut banks or dense trees within 10 yards or so. The latter criterion is probably about call transmission -- the farther onshore they can be heard, the better, since females are foraging away from the streambed until they decide to breed. The stagnation thing is harder to explain but probably has to do with egg and larval survival. You won't find toads calling (or fresh clutches) in side channels that are no longer linked to the stream -- places like that are sometimes used until their connection dries, but thereafter abandoned. It makes some sense to avoid them, since they often dry up well before tadpoles can mature, and in those situations the tads are sitting ducks for garter snakes and other predators.

If the inflow area of a beaver pond meets those criteria I wouldn't be surprised to see arroyo toads use it.

Re: SoCal Endangered species herping, part 4

Posted: August 29th, 2010, 11:06 pm
by Paul White
is there any way to do trasmitters on them at all? the thought of something that size transversing that sort of distance, in that sort terrain is mind boggling! Maybe a mark/recapture even, at each supposed location to see if the same animal winds up at them?

Re: SoCal Endangered species herping, part 4

Posted: August 30th, 2010, 7:54 am
by justinm
Sam I really appreciated this writeup, thanks a lot. It's exactly what I would like to see in HerpNation.

Re: SoCal Endangered species herping, part 4

Posted: August 31st, 2010, 3:22 pm
by Jackson Shedd
Very, very cool post, Sam. I really dig all the comparison photos, but I really appreciate the lesser known information you've supplied here.

Re: SoCal Endangered species herping, part 4

Posted: September 1st, 2010, 4:53 pm
by Crotalus
Sam Sweet wrote:Arroyo toads are members of the Bufo americanus species group, which is basically limited to regions with reliable summer rainfall – B. californicus in southern California is a relict of wetter conditions that ended 10-12,000 years ago, and it really should not still be present in a region where annual rainfall of 20” or less occurs only in the winter months. It has been able to persist owing to some unusual topographic features.
Even Bufo microscaphus and B. mexicanus breed during the spring, right? How does that work?

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 4:05 pm
by Sam Sweet
Even Bufo microscaphus and B. mexicanus breed during the spring, right? How does that work?
Pretty much the same way, at least for low-elevation populations of B. microscaphus -- no one knows much at all about the biology of B. mexicanus. Where B. microscaphus occupies streams draining higher parts of the Colorado Plateau there can be appreciable runoff from snowmelt in the early part of the breeding season. Thereafter it's much the same story -- a landscape structured by much higher erosion rates during glacial periods, whose streams are presently incompetent to transport the sediment load they hold, with a lens of stored groundwater in the canyon fill.

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 4:54 pm
by Joseph S.
Sam: Suppose you microchipped animals and then set up something that could scan for microchips and place these in special retreats(artificial retreats) that would scan incoming toads for microchips. Placing these around the mountain and near hypothesized routes might give an idea of any movement occuring. Of course you'd need a lot of them(readers and microchips) and I don't know if such a battery operated reader exists.

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 5:24 pm
by JakeScott
Nice post. Thanks for the comparative photos and some background info. Those are cool tow-ads!

-Jake Scott

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 9:35 pm
by FunkyRes
Joseph S. wrote:Sam: Suppose you microchipped animals and then set up something that could scan for microchips and place these in special retreats(artificial retreats) that would scan incoming toads for microchips. Placing these around the mountain and near hypothesized routes might give an idea of any movement occuring. Of course you'd need a lot of them(readers and microchips) and I don't know if such a battery operated reader exists.
One idea would be solar cells to recharge the batteries.
It sounds like needle in a haystack, but it would be neat if it worked.

There are roads they cross? Would PVC tunnels under the roads with a scanner at entrance entice some of them to cross the road that way, avoiding splatter and getting scanned at same time? I've seen them using ground squirrel networks in Contra Costa County, though that may have just been for shelter.

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 10:29 pm
by Sam Sweet
Let's suppose you wanted to test the idea that Bufo boreas were making long-range movements, based on finding adults crossing a ridge in one direction in early summer and back in winter, coupled with knowing that there are no breeding sites anywhere on the ridge. It wouldn't be easy, based on a sample photo of the Santa Ynez range here. The elevation gain averages about 2,000' on a minimum path of 1.5-2 miles, nearly all in mature chaparral that is relatively open at toad level, but nothing you'd want to tackle on foot.

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You could identify individual breeding or ridge-crossing toads with PIT tags, toeclips, or maybe just photos of dorsal pattern variation, but the trick is finding them again someplace else -- to have a reasonable shot at it you'd need to mark a few hundred breeders then try to intercept a serious number on the ridgeline, or mark every one you could on the ridge then sort through hundreds along the river. Maybe they follow canyons, maybe ridges, maybe they just go "up" or "down" any old way they feel like, you wouldn't know. Even one hit would prove the principle, but it'd be a huge time investment just to turn a maybe into a yes.

You could learn a lot by radiotracking animals, but that's expensive and labor-intensive, even if you could get a radio to stay attached to a toad and transmit for 4-6 months. To get some idea of the challenge in that, I've added in the approximate reception range of the most powerful unit I think you could put onto an adult toad. It's clear that you wouldn't be standing long in the river or on the crest before you lost the signal even if conditions were ideal (mostly, they won't be!). Assuming you haven't got $600-800/hr for a helicopter, radios wouldn't be much use. Remote PIT tag readers (each costs as much as 3-4 radios) would only be feasible if you knew places where animals would pass within 3-6", and if you knew that already you wouldn't need the readers, eh.

I've gone through this example to give some idea of how challenging it can be to answer many very simple questions about herp behavior. The backside to that point is that we may often underestimate the kinds of things these animals can do, just because we can't keep track of them for long enough or far enough to identify their capabilities.

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 11:40 pm
by Crotalus
Have you considered using Frank Retes to follow the toads and decipher their feelings and plans?

-JJ

Re: SoCal Endangered species herping, part 4

Posted: September 2nd, 2010, 11:55 pm
by FunkyRes
I definitely can identify.
I know what it is like to go through mature chaparral.

Early July I got dropped off where pavement ended and was following a dirt road for just over 10 miles to get my Rana cascadae. On the way, I found a small stream and followed it off road, and my GPS showed one of my marked waypoints was within a mile or so of where I was, I thought I could shave some time by cutting through the chaparral.

It took me 3 hours to do less than half a mile, and I was cut completely to shreds, hyper-ventilating, I was in really bad shape.

The only plus is I got my Yellow-bellied Racer and found an absolutely killer rock outcropping that I know has zonata - and nobody visits that outcropping, nobody. No shot gun shells, beer bottles, or any other signs of the deer hunters that frequent that area. It's a huge outcropping but it is completely surrounded by chaparral. It looks just like all the pictures from killer zonata spots.

I have marked that outcropping and have found a way to get close to it, so when I return next year to camp at it during right time of year, I'll only have a little chaparral to have to fight through. It will be rough, but I just know I'll get a Z from it.

But cutting through chaparral for any distance is definitely not something I ever want to do again. That stuff is not forgiving.

Re: SoCal Endangered species herping, part 4

Posted: September 3rd, 2010, 8:05 am
by Fieldnotes
I'm not entirely sure how i missed this post (I must be spending too much time solely on the California forum), cause this is the best Arroyo toad post EVER!!! :thumb: :thumb:

Re: SoCal Endangered species herping, part 4

Posted: September 3rd, 2010, 9:25 am
by hellihooks
FunkyRes wrote:I definitely can identify.
I know what it is like to go through mature chaparral.

Early July I got dropped off where pavement ended and was following a dirt road for just over 10 miles to get my Rana cascadae. On the way, I found a small stream and followed it off road, and my GPS showed one of my marked waypoints was within a mile or so of where I was, I thought I could shave some time by cutting through the chaparral.

It took me 3 hours to do less than half a mile, and I was cut completely to shreds, hyper-ventilating, I was in really bad shape.

The only plus is I got my Yellow-bellied Racer and found an absolutely killer rock outcropping that I know has zonata - and nobody visits that outcropping, nobody. No shot gun shells, beer bottles, or any other signs of the deer hunters that frequent that area. It's a huge outcropping but it is completely surrounded by chaparral. It looks just like all the pictures from killer zonata spots.

I have marked that outcropping and have found a way to get close to it, so when I return next year to camp at it during right time of year, I'll only have a little chaparral to have to fight through. It will be rough, but I just know I'll get a Z from it.

But cutting through chaparral for any distance is definitely not something I ever want to do again. That stuff is not forgiving.
Boy you ain't kidding! Most of the berdoos are chaparral... which might explain why the hi-ele rosys from there are basically only known from museum specimens... but I WILL find one next spring... if I gotta camp out up there for a month! And flip a Z... :roll: :lol: jim

Re: SoCal Endangered species herping, part 4

Posted: September 7th, 2010, 9:36 am
by RockRatt Rich Morgan
Sam I too think this would be an EXCELLENT article for HerpNation. I am not so much a frog/toad guy but have been intrigued this season even going to a small pond every few weeks in springtime photo'ing transformation from tads to toadlets just because I thought it was neat and my son would like it. Your explanations here DO give a great read and more to think/look at when I find certain toads. Thanks for some great info and I would love to read ALL the info at one time in HerpNation. Most snake guys do find frogs/toads just with the type of searching so it would be excellent knowledge to have on hand.