Dicamptodons in still water?

[noneofmany]

I recently visited a pond store in monroe (to which I recently moved) and struck up a conversation with one of the staff. Upon asking about if she's ever seen a newt or salamander in her ponds she immediately told me that there were "water dogs" the size of subadult koi in all of their deeper fish ponds. She also said she was surprised that the west coast had water dogs too!

I was kind of stunned when she told how many there were in any given pond. Appearantly they pull them up buy the dozen when the largest pond is drained out for maintenance.

They also seem to be eating the koi, because the fry always seem to disappear before they get very big. As such, only adult koi remain in the pond.

I never really thought of dicamptodons as pond caudates. But I guess I was wrong. Big ones can actually live their whole lives in still water.

It's also interesting that the ponds have bull frogs, most of which are very mature adults, but there aren't many of them in deeper, permanent pools where she says she sees the 12 inch plus water dogs. But in adjacent kiddy sized pools theres often ten or twelve of every different size. Are the giant salamanders eating the frogs and there tadpoles? She seemed to say that was the case since as time goes on the population of frogs and tadpoles plummets but the salamanders remain.

I never thought that the two large amphibians shared the same habitat but since I now know otherwise I can only assume that there is some predation going on between them, and it seems, it's mostly the salamanders that doing the predation part. The presence of both koi and bullfrogs has not stopped the dicamptodons from populating the ponds. At least one native herp is able to compete with the bull frogs!

Anyone have any thoughts on this? Has anyone seen evidence of bull frogs getting eaten by giant salamanders, or coexisting with them.

I actually remember seeing a dicamptodon rising to surface of a stream to grab a swimming frog. It was just tree frog, but given their size and toothy nature I can certainly imagine one grabbing a bull frog.

 

[otolith]

While I don't doubt there is some sort of salamander in these ponds I am a little dubious about them being Dicamptodon if Ambystoma aren't in the area. It seems more likely to me she is finding large Ambystoma larvae rather than neotenous adult Dicamptodon. That being said, in my experience I have not seen many DIcamptodon in still water. I can definitely picture a pond full of large Ambystoma larvae laying waste to a school of baby koi.

My neighbors have a small pond they stock with trout that gets a good breeding of T. granulosa most years. I have never found D. tenebrosus there but have found morphed adults at our house across the street and in a temporary creek nearby. Anecdotal evidence isn't really concrete of course, but being that D. tenebrosus is common in my area but only in streams seems to be noteworthy.

I don't think any but the very largest adults would be able to eat adult bullfrogs. The only instance I've seen bullfrogs in Dicamptodon habitats are at one location where a stream with D. tenebrosus flows into a lake with bullfrogs. There is a narrow zone where the two overlap but the seasons where they are most active do not really overlap. I bet they are eating lots of yellow legged frog tadpoles and juveniles all across the state though.

Its definitely an interesting bit of info from the Store clerk though,and if true is kind of a game changer as far as suitable habitats. I am skeptical though, I wish she had shown you some pictures.

 

[sde]

I would be surprised if it was actually D. tenebrosus. A. gracile, however, is a definite possibility. They can become neotenic and can get quite large, up to 8 or 9 inches. Also, D. tenebrosus needs cool water, and I doubt that the water in these ponds stays very cool in the summer time. I am not saying it is impossible, but I do find it quite unlikely.

As for the bullfrogs, in my experience bull frogs don't go into very deep of water unless they feel threatened. This could explain why there aren't as many in the deeper pools. Plus, in the shallow ponds the water will be warmer, so they would be likely to frequent them more often for that benefit.
The salamanders could eat the tadpoles, but I cant imagine one eating a full sized adult. Most of the adults here in my area are massive, 5 inches total length easily, and very fat and muscular. I don't think even a D. tenebrosus could get that down their throats, unless they ate it piece by piece....but they would have to take a limb off before the frog could escape, and knowing how strong these frogs are ( I once had two hands pinning one to the ground and it forced its way out ), I just don't see it happening.

When you say she says that as time goes on the bullfrog population plummets, do you mean over the course of a few years, or within one year?

Also, in the ponds near my house there is a large population of bullfrogs, and yet A. gracile populations are doing fine. This is another reason I think that the salamanders are A. gracile.

I mean, I suppose it is possible they are D. tenebrosus, but all these things together - them being in ponds, the presence of koi, the presence of bullfrogs, most likely warmer water - I feel it is more likely it is a different species, and my best guess would be A. gracile.
-Seth

 

[noneofmany]

I would be surprised if it was actually D. tenebrosus. A. gracile, however, is a definite possibility. They can become neotenic and can get quite large, up to 8 or 9 inches. Also, D. tenebrosus needs cool water, and I doubt that the water in these ponds stays very cool in the summer time. I am not saying it is impossible, but I do find it quite unlikely.

As for the bullfrogs, in my experience bull frogs don't go into very deep of water unless they feel threatened. This could explain why there aren't as many in the deeper pools. Plus, in the shallow ponds the water will be warmer, so they would be likely to frequent them more often for that benefit.
The salamanders could eat the tadpoles, but I cant imagine one eating a full sized adult. Most of the adults here in my area are massive, 5 inches total length easily, and very fat and muscular. I don't think even a D. tenebrosus could get that down their throats, unless they ate it piece by piece....but they would have to take a limb off before the frog could escape, and knowing how strong these frogs are ( I once had two hands pinning one to the ground and it forced its way out ), I just don't see it happening.

When you say she says that as time goes on the bullfrog population plummets, do you mean over the course of a few years, or within one year?

Also, in the ponds near my house there is a large population of bullfrogs, and yet A. gracile populations are doing fine. This is another reason I think that the salamanders are A. gracile.

I mean, I suppose it is possible they are D. tenebrosus, but all these things together - them being in ponds, the presence of koi, the presence of bullfrogs, most likely warmer water - I feel it is more likely it is a different species, and my best guess would be A. gracile.
-Seth

Actually the pools are very suitable for bull frogs. They have water about three to four feet deep and many kinds of floating plants all over place. I was told the waters depth, shade from plants, and the streams that flow into them keep the water cool year round. He said they must do this because their high fin sharks need it 65f or below.

Another thing that points to dicamptodons is that the artificial streams that feed into the pools are where allot of them like to hang out under rocks. That water is very shallow and very fast moving, I don't think the D. Gracile ever occupy that habitat.

As for the bull frogs, when I say they plummet I mean the number juveniles never increases. There's tadpoles and neonates at the beginning of the year but the only remaining frogs at the end are the big mature adults. I don't think they eat the adults, but the tadpoles and sub adults just keep disappearing.

Likewise in one of the pools that has many koi but no salamanders there are plenty of frogs of all age groups.

 

[Chinadog]

Maybe its the Koi that are eating the fry and tadpoles? Adult carp are more than capable of eating the largest of tadpoles, even Bullfrog ones. Mine will eat anything that's not screwed down and although they look like big lazy pigs, they are surprisingly fast and agile if they are hungry.

 

[noneofmany]

Maybe its the Koi that are eating the fry and tadpoles? Adult carp are more than capable of eating the largest of tadpoles, even Bullfrog ones. Mine will eat anything that's not screwed down and although they look like big lazy pigs, they are surprisingly fast and agile if they are hungry.

I thought that at first as well. But they also have two stagnant ponds as well with koi in them and there's far more frogs. There's also a small pond with virtually no plants or cover for them that's practically the size of a puddle with like eight sub adults sitting in it.

Likewise, an adjacent pond has no koi, lots of plants, and more sun. However, it also apparently has a lot of sals and it's virtually devoid of frogs except for a huge female who seems to mostly stay out of the water.

The ponds where they see the largest concentration of salamanders are very heavily aerated and have quite a bit of movement and waves. Unlike many other ponds, one of them has a rocks and pea gravel bottom. The waters flows around a fair amount and, thanks to a triple waterfall, is so aerated that the water is sort of turbid and whitish from all the tiny bubbles.

This maybe why the dicamptodons favor them. There not very different from a still pool I once saw one attack a frog in. That body of water was a wide flat area with a stream inlet on one side and a stream draining water out on the other. The water was still and about three to four feet deep, like a pond.

Interestingly enough I happened to speak a friend of mine about this and he said that he knew a man that had actually caught a dicamptodon to put in his artificial stream that fed into koi pond. At first it stayed and fed in the stream section, but after a while it headed into the deep end of the pond where it remained until it was netted and placed back into the stream (it ate a goldfish) where mesh barriers were put in place to prevent it from leaving. It remained their for several years attained a length of 11in before a heron got it.

So, I have one other example of a dicamptodon entering deep still water and remaining, and feeding there.

 

[sde]

Actually the pools are very suitable for bull frogs. They have water about three to four feet deep and many kinds of floating plants all over place. I was told the waters depth, shade from plants, and the streams that flow into them keep the water cool year round. He said they must do this because their high fin sharks need it 65f or below.

I didn't say that the pools weren't suitable for the bullfrogs, I just mean that they might not frequent them as much because it may not be as warm.
You didn't tell me that there is a stream flowing into it! That would make it a lot more likely that they are D. tenebrosus.

As for the population of tadpoles, the salamanders could be eating them, like you say, I never said they couldn't be.

 

[otolith]

I am still skeptical. Very few artificial ponds are going to have enough of a creek portion to provide suitable habitat for multiple adult Dicamptodon. These creek portions would also be unusable for young koi. Also the fact that she said "waterdogs" and not Pacific Giant Salamanders means it could be anything. Ambystoma still seem more likely to me. I believe in the bullfrogs though

 

[Chinadog]

Perry, is it the shallow creek sections that the Decamptodons need, or the dissolved oxygen content of the water itself? If its a well designed system specifically for Koi the oxygen content will be high, mine runs at 9mg/litre throughout the summer.
I do agree that the salamanders are unlikely to be Decamptodon, but I also find it quite amazing that any aquatic salamanders would live and even breed alongside koi! I would love to find out for sure what they are.

 

[otolith]

Perry, is it the shallow creek sections that the Decamptodons need, or the dissolved oxygen content of the water itself? If its a well designed system specifically for Koi the oxygen content will be high, mine runs at 9mg/litre throughout the summer.
I do agree that the salamanders are unlikely to be Decamptodon, but I also find it quite amazing that any aquatic salamanders would live and even breed alongside koi! I would love to find out for sure what they are.

It is a combination of those factors. For me though, the primary things that keep tugging at my brain are the amount of space needed to provide adequate forage for a group of DIcamptodon larvae and the time it takes for these animals to grow. First a group of Dicamptodon would have to choose the pond over their natal stream to spawn. Second, if spawning were successful the eggs and larvae would have to avoid detection from a high density of koi who feed by rooting through the substrate where these eggs are laid. Third, these survivors would need to live in the pond for 2-4 years to get to the sizes mentioned. These are all possible of course, but unlikely. Throw in a few more variables like a pond maintenance crew draining the pond every year or so and it feels even less likely for such a large, slow growing caudate to become established.

An explosive breeder like Ambystoma gracile that lays mass amounts of eggs, spawns in still water, grows rapidly to morphing size and has a widespread distribution seems much more likely.

I would also love to know what they are though, if they are truly D. tenebrosus that would be amazing.

 

[Chinadog]

The easiest part to imagine is the salamander larvae settling in the filter beds for the pond. Depending on how the system is designed the filter beds could support a large head of larvae. The water will be quite fast moving and highly oxygenated, probably more so than the pond water to maximise bacterial growth to clean up after the fish. Also if its an older type the pre filter area will be crawling with bloodworm and scuds etc living in the silt. If the larvae are mostly in the filter beds, it would nicely explain how they avoid being pumped away during maintenance/draining of the pond itself?

 

[Salmonidae]

I agree with Seth that they are most likely A. gracile based on the location (Monroe) and habitat described. Searching the Washington Herp Atlas,
I believe that it is possible however that they could be D. Tenebrosus but not likely D. copei. D. Tenebrosus have been documented living in slow water "pond" habitats adjacent to moving streams if the water remains cool and oxygenated, however they typically return to moving water to breed.

 

[noneofmany]

Ok. I got a good break in this case. I spoke with the store manager and she said she'd call me the next time they drain the largest pool for maintenance. She said they always find several of them when they do it and wouldn't mind if I came over to watch.

So I should be able to settle this some time in the next several months.

Until then I can't say even I completely believe there dicamptodons either, especially after all your guys great feed back. I'm still, however, not too skeptical since I have personally seen dicamptodons in deep, well oxygenated, but still pools along side adult trout. Pools that were very similar to these artificial ones. In fact the the first time I ever even saw a dicamptodon was when one suddenly rocketed up through the water column (in waste deep water) to grab a swimming frog.

Before I heard about the man who collected a specimen having it leave the stream to eat fish in the lower pond, I figured the one in the pool was just an unlikely oddball. Maybe not though.

Amusingly, that incident scared my father who was standing in the stream practically right on top of where it came up. He has a moderate phobia of snakes and eels, so when it came up right in front of him he was quite startled and stumbled back a bit. If he hadn't yelled out to me I would not have turned around in time to see it diving back down with the poor frog (which was there because that's were we had just released it ) and duck under a log by my dad's foot.


Even so I can't believe that these guys are living with full grown koi. I mean, I know I've seen them with medium sized trout, but it still amazes me they can live with multiple two foot plus koi for long enough to grow to adults!

 

[knifegill]

Mine's just in a 10g with an air-powered sponge filter on deep sand bed and wads of aquatic plants. Not much current to speak of. He's been happy in there over a year, not long, but he is growing happily.