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 Post subject: SoCal Endangered species herping, part 3
PostPosted: July 27th, 2010, 8:46 pm 
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Sometimes a fella gets sick of slopping in mud after tiger salamanders and remembers that streams are much cleaner places to get wet. In that case it’s toad time. A student in my lab is gearing up to work on tadpole ecology, so we have been revisiting a number of places where I worked on arroyo toad biology a few years ago. In this post I’ll cover breeding biology, tadpoles and juveniles of arroyo toads and western toads, and defer saying much about the natural history of adults to a later post.

Western toads (Bufo boreas) are declining but still widespread in coastal southern California, and will breed in almost body of water. Arroyo toads (Bufo californicus) have much narrower habitat requirements, and are restricted to sediment-choked middle reaches of major drainages. About 70% of the original extent of this habitat has been alienated by dams, channelization and floodplain development. Surviving arroyo toad populations are isolated and face a host of other deleterious changes, and the species has been federally listed as Endangered since 1994. This has certainly helped change land- and water-management activities, but things like chytrid fungus, bullfrogs and exotic fishes are really poor at reading regulations, so the species is hardly doing well overall.

In streams where both toad species occur B. boreas begins breeding 3-5 weeks earlier. Male western toads don’t really call (they will chirp), but instead patrol pools trying to be the first to intercept an arriving female (and will grab almost anything of the right size). As in most toads the female then carries the male to an egg deposition site of her choosing. For B. boreas in streams this is usually a steep bank edge lined with tipped-over bushes, cattails or some other sort of dense cover, and the egg strings are soon hopelessly entangled.

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Bufo californicus wait until flooding is less likely. Males set up calling stations along open pool edges where the water is less than about 3” deep and has little current. Females select a male to approach (the largest they can hear wins), and the clutch is laid at the male’s calling site. Since males use the same site for weeks, there can be several clutches of various ages grouped in a small area. Unlike B. boreas, B. californicus eggs aren’t attached to anything, and simply lie on the bottom in very shallow water. This makes them susceptible to stranding or being washed away if the water level changes much over the next week or ten days.

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Toad clutches are double-stranded (one string from each oviduct), and the jelly layer absorbs water and collects silt, so that you can estimate the age of many clutches just by looking at them. Here are three arroyo toad clutches of varying ages:

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Bufo eggs and newly-hatched tadpoles are toxic courtesy of bufotoxins deposited in the yolk by the female, but older tadpoles lose the toxin and do not make their own until metamorphosis. Egg masses and aggregated small tadpoles are typically ignored by vertebrate and invertebrate predators alike.

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Tadpoles of both species hatch several days before they can swim, and remain very vulnerable to water level changes.

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Tadpoles of both species are initially solid black, and can be hard to identify except by making an assumption from the deposition site. While they are still less than about 12 mm TL, B. boreas tadpoles tend to be oval (vs. slightly pear-shaped) and have longer tails that seem more flexible (vs. shorter and stiffer). Behavior is also a good cue – in a group of small boreas tads about a quarter of them will be active at any moment, whereas small californicus tads tend to be very still, only a few out of hundreds swimming at any instant. The upper clutch here is probably B. boreas, that in the lower left probably B. californicus, both by deposition site and size of the newly-hatched larvae.

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Larval B. californicus very soon start to develop pale areas on the top of the tail, and white patches near their little bottoms, and thereafter the two species are quite easy to distinguish. Early on, you often see mixed groups that sort out later.

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The risk of flooding is low after mid April, and tadpoles distribute themselves across the streambed. Four species are native in most streams (Bufo boreas and B. californicus, Pseudacris cadaverina and P. regilla), but we are missing the native Rana species (R. boylii and R. draytonii), which are regionally extinct.

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I won’t have much to say here about ecological differences among these species as tadpoles, but they definitely tend to use different parts of the stream channel (based on depth, temperature, current and bottom type), and are probably feeding on different algal communities. There can be a lot of tadpoles, and shallow pool edges can be quite warm by day (80-90 F), so they grow very quickly and are major consumers.

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Western toad larvae change color as they age, and become relatively cryptic, while arroyo toad tadpoles are very cryptic from an earlier age

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This shot below is a repeat from the crashed forum – there is one western toad, but how many arroyo toad tadpoles are there?

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Many of these streams go dry in a hurry beginning in mid July, and tadpoles have to metamorphose quickly to avoid becoming dinner.

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Metamorphosing tadpoles are actually easier to tell apart than are juveniles. In the composite photo below the western toad (top) is darker, with larger, brick-red tubercles, and without the pale V on the eyelids or light areas over the sacral humps that distinguish arroyo toad metamorphs.

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Once they are out of the water for a few days, the juveniles tend to sort themselves into characteristic microhabitats. For example in the streambed shown below, western toad juveniles would either be dug into the wet sand at the pool edge, or in the shade of vegetation, whereas the juvenile arroyo toads are smack out on the exposed bar in full sun. They are active and foraging all day, but burrow in at night, whereas the western toads almost immediately become nocturnal.

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A couple of western toads, followed by some arroyo toads.

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Yes, the juveniles are hard to tell apart, but that’s a story for later.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 27th, 2010, 10:02 pm 

Joined: June 7th, 2010, 12:37 pm
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Location: Ft. Smith, Arkansas
Another great CA amphib post, Sam.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 27th, 2010, 11:13 pm 
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Awesome post! Thanks for the information. I encountered my first Arroyo a few weeks ago shortly after a storm. It was definitely an exhilarating feeling finding one!


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 5:33 am 
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Another Awesome post... Thank you sir..

My favorite line
Quote:
but things like chytrid fungus, bullfrogs and exotic fishes are really poor at reading regulations


Fundad


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 6:43 am 
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Great detailed information about the differences in tadpole behavior, thanks for taking the time to put this together!


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 7:24 am 
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Sam: I noticed that you still refer to both these species as "Bufo". What's your take on the reclassification to "Anaxyrus"? I hear alot of conflicting opinions and really don't know what to conclude. It's also hard for many Californians to imagine how much boreas is in decline in other states such as Utah and Colorado given the fact how ubiquitous it is here in CA.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 7:47 am 

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Really neat post, Sam. Thanks for taking the time!

-JJ


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:06 am 
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Good stuff big fella. Still waiting for you to make a post on New Guinea!


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:15 am 
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klawnskale wrote:
Sam: I noticed that you still refer to both these species as "Bufo". What's your take on the reclassification to "Anaxyrus"? I hear alot of conflicting opinions and really don't know what to conclude. It's also hard for many Californians to imagine how much boreas is in decline in other states such as Utah and Colorado given the fact how ubiquitous it is here in CA.


I wouldn't call them "ubiquitous" - they're in decline in California too. For example, in the LA Basin I can't find them until I get to the foothills of the San Gabriel Mountains, even though I know a number of locales where they were historically abundant.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:36 am 

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I think I counted 20 in that photo. Am I even close?


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:45 am 
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jonathan wrote:
klawnskale wrote:
Sam: I noticed that you still refer to both these species as "Bufo". What's your take on the reclassification to "Anaxyrus"? I hear alot of conflicting opinions and really don't know what to conclude. It's also hard for many Californians to imagine how much boreas is in decline in other states such as Utah and Colorado given the fact how ubiquitous it is here in CA.


I wouldn't call them "ubiquitous" - they're in decline in California too. For example, in the LA Basin I can't find them until I get to the foothills of the San Gabriel Mountains, even though I know a number of locales where they were historically abundant.


That's a ridiculous assumption. I find them regularly here in the San Fernando Valley in the foothills and in the Santa Monicas. I know waterways in this area that had good tadpole density this Spring. It's not my problem if you have an aversion to the San Fernando Valley. Oh, you never contacted me about volunteering on the Nerodia. Don't like getting dirty? :lol:


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:47 am 
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Yeah, I suppose they ought to be called Anaxyrus (or at least something other than Bufo), but nobody was confused, right? I am much more convinced about placing cadaverina and regilla in Pseudacris, since that makes both Hyla and Pseudacris much easier to characterize morphologically, behaviorally and ecologically. The problems with large-scale phylogenetic reconstructions such as that giving us Anaxyrus, Lithobates, etc., are at least two. (1) The choice of characters (both gene sequences and morphology) can strongly influence branch order and groupings when you're trying to find the best fit among hundreds or thousands of "most parsimonious trees" that differ by an insignificant number of steps. (2) If the generic-scale groupings are at all fuzzy, more detailed and focused analyses often separate out some basal lineages, which may merit recognition as separate genera. This carries some likelihood that a different, more recently-applied generic name would be resurrected for the remaining species.

In other words, no matter how careful and inclusive an initial analysis might be, folks like me who have to consider relabeling entire collections and databases have learned to wait a bit, until subsequent analyses confirm the rationale for altering generic names. All you need to do (for example) is look at the ebb and flow of "definitive analyses" about partitioning the genus Clemmys -- which species belong in Clemmys, Emys, Emydoidea, Glyptemys, Actinemys ...? Pretty much every possible combination has been advocated by one group or another. I do think that Anaxyrus is a valid genus for *some* group of species of toads, I'm just not yet convinced that membership won't change.

Everyone wants classification to reflect evolutionary relationships accurately, but it's often not as simple to reconstruct that history from the species that are present now as one might like to think.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:54 am 
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Sam Sweet wrote:
Yeah, I suppose they ought to be called Anaxyrus (or at least something other than Bufo), but nobody was confused, right? I am much more convinced about placing cadaverina and regilla in Pseudacris, since that makes both Hyla and Pseudacris much easier to characterize morphologically, behaviorally and ecologically. The problems with large-scale phylogenetic reconstructions such as that giving us Anaxyrus, Lithobates, etc., are at least two. (1) The choice of characters (both gene sequences and morphology) can strongly influence branch order and groupings when you're trying to find the best fit among hundreds or thousands of "most parsimonious trees" that differ by an insignificant number of steps. (2) If the generic-scale groupings are at all fuzzy, more detailed and focused analyses often separate out some basal lineages, which may merit recognition as separate genera. This carries some likelihood that a different, more recently-applied generic name would be resurrected for the remaining species.

In other words, no matter how careful and inclusive an initial analysis might be, folks like me who have to consider relabeling entire collections and databases have learned to wait a bit, until subsequent analyses confirm the rationale for altering generic names. All you need to do (for example) is look at the ebb and flow of "definitive analyses" about partitioning the genus Clemmys -- which species belong in Clemmys, Emys, Emydoidea, Glyptemys, Actinemys ...? Pretty much every possible combination has been advocated by one group or another. I do think that Anaxyrus is a valid genus for *some* group of species of toads, I'm just not yet convinced that membership won't change.

Everyone wants classification to reflect evolutionary relationships accurately, but it's often not as simple to reconstruct that history from the species that are present now as one might like to think.


I can understand, why you'd want to wait and let the 'dust' of reclassification to settle. Kind of like waiting for the second or third generation of a software after all the 'bugs' are worked out.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 9:58 am 
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klawnskale wrote:
jonathan wrote:
klawnskale wrote:
Sam: I noticed that you still refer to both these species as "Bufo". What's your take on the reclassification to "Anaxyrus"? I hear alot of conflicting opinions and really don't know what to conclude. It's also hard for many Californians to imagine how much boreas is in decline in other states such as Utah and Colorado given the fact how ubiquitous it is here in CA.


I wouldn't call them "ubiquitous" - they're in decline in California too. For example, in the LA Basin I can't find them until I get to the foothills of the San Gabriel Mountains, even though I know a number of locales where they were historically abundant.


That's a ridiculous assumption. I find them regularly here in the San Fernando Valley in the foothills and in the Santa Monicas. I know waterways in this area that had good tadpole density this Spring. It's not my problem if you have an aversion to the San Fernando Valley :lol:


I'm not talking about the foothills in the San Fernando Valley (didn't I say I find them in the foothills?) or the Santa Monica Mountains. I'm talking about down in the Basin. I've been to many historic localities in the South Bay and through central Los Angeles and have not found them anywhere in recent years - have you? I can name locations in Palos Verdes, Torrance, and La Mirada where they were found in recent memory but appear to now be extirpated, and I've been to other locales where they don't seen to be around but I don't know enough information to say they're gone completely yet.

In fact, I just now looked at the museum databases and confirmed that western toads have been recorded historically over pretty much the entire LA Basin. If they weren't in decline, then every one of those spots that has chorus frogs and bullfrogs in it today would still have toads as well.

Just because they're abundant in some locations does not mean they're not in decline in others.


p.s. - another historic locality is Harbor Lake and the surrounding area. Have you seen any toads there yet? I would love it if they've held on, but I'm not holding out any hope.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 10:07 am 
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I wouldn't call boreas ubiquitous any more in coastal southern California, having seen them slowly disappear from many places on the suburban fringe. Apart from progressive loss of habitat and habitat connectivity, I think that road mortality plays quite a role. Adult western toads are great wanderers, and they are attracted to open ground to forage at night. Increases in traffic affect the big breeders most, and after a while there aren't any left.

This was an acute problem for arroyo toads where access roads and drive-in campgrounds were situated on stream terraces -- the toads love roads as foraging sites and travel paths, and on summer weekend nights one vehicle after another would circle the whole area looking for an open campsite. No luck for them, and no luck for the toads.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 10:23 am 
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klawnskale wrote:
Oh, you never contacted me about volunteering on the Nerodia. Don't like getting dirty? :lol:



Hey, I pulled my last three water snakes out of that lake by going briefly barefoot, so don't call me out on dirtiness! (btw, that was stupid, thank God I just got my hepatitis shot :lol: ). I contacted Mark about borrowing waders and gloves, and he thinks he has something that will work for me, so I'm planning to go out with him first and then be able to be fully equipped when I meet up with you.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 10:38 am 
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p.s. - another historic locality is Harbor Lake and the surrounding area. Have you seen any toads there yet? I would love it if they've held on, but I'm not holding out any hope.[/quote]

I will be doing a visual night survey of the lake Thursday evening with another field tech. If boreas is there, we would most likely see them at night. A local homeless man claims he saw one by the description he gave of the animal. I will ofcourse, be taking pics.
Believe it or not there are also Cal Kings around there. Two reliable sources have seen them there. There is even a boardline there that the homeless people know about. I wonder if it's a Hubbs?


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 12:14 pm 

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Good stuff again Sam. I'll be down that way in a couple weeks, hopefully I'll have time to stop by campus.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 4:03 pm 

Joined: June 7th, 2010, 4:48 pm
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More great stuff, and another set of excellent comparison photos, Sam. Although a post of this nature is very interesting for many, it's also a very useful tool for someone in my line of work. Keep 'em coming!


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 28th, 2010, 10:02 pm 
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Another information packed post, as usual. Thanks for sharing your knowledge of these toads.

Todd


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 29th, 2010, 10:27 am 
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your posts are cool... keep them coming :thumb:


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 29th, 2010, 2:43 pm 
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Really great info here Sam. Arroyo Toads are a species that I have no experience with, so this was particularly interesting to me. Thanks again!


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 29th, 2010, 8:46 pm 
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Nice description for sure, I counted 19.

Cheers
Lat


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 29th, 2010, 9:42 pm 
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Pretty sure there are 22 B. californicus and the one B. boreas in the frame:

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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 29th, 2010, 10:19 pm 
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Wow...the first time I counted I found 21 and 1. Even now, knowing there are 22, I can still only find 21.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 30th, 2010, 8:15 pm 
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Great post! Really interesting read.


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 Post subject: Re: SoCal Endangered species herping, part 3
PostPosted: July 31st, 2010, 9:16 pm 
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Nice ! life cycle post. Awesome!


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