Neurergus experiment: aquatic vs. terrestrial

In October 2003 I obtained a group of N. s. strauchii juveniles (recent metamorphs). In March 2004 I acclimated 4 of them to an aquatic setup by first placing them in very shallow water thick with plants. When they showed that they were willing to stay in the water (eating, and no climbing), I moving them to a deep water setup with mainly rocks. The remaining 4 were kept terrestrially.

Today I photographed one animal from each group. Each of these animals is very typical of the others, and among the largest of each group. First, two photos of a terrestrial one, then two photos of an aquatic one.









There are some interesting differences.
(1) The aquatic ones are larger.
(2) The aquatic ones have a more "adult" coloration (extra spots are developing).
(3)The terrestrial ones are distinctly orange, while the aquatic ones are yellow. Both are offered the same foods (blackworms and earthworms, with occasional crickets and fly larvae). The terrestrial ones probably eat more blackworms.

Anyone have any other observations? Any idea about sex, based on these photos? Any idea how close they are to breeding size?

Nice experiment! I think the aquatic ones should be able to breed next year. I should have to look how large mine were when they started with reproduction. I'll be back on that.

Well Jen, that's odd.. I just had the inverse experiment in Neurergus strauchii stracuhii when raising mine. The ones in a leaflitter setup got larger then the ones kept aquatic... Also one escaped N. crocatus juvenile recaptured in the spring thereafter surpassed all of it's brothers and sisters whether they were kept aquatic or terrestrial.

Maybe the setup is not the most critical topic and other criteria are more important like food and temperature differences. The animals I kept always grew quickly during the fall and winter and kind of stopped growinng during the summer and spring. In Hynobius growth is also temperature related (when too warm all energy goes to sustain the life rythm).
But it is strange to see yuo get exactly the opposite outcome then I did.

I notice that the aquatic N. strauchii eat a lot more food, in total. I hand-feed them almost every day, and also leave small worms in the tank for self-feeding. I think that aquatic life takes a lot more energy.

Aha, there is a crucial point. If you feed the aquatic ones every day and the terrestrial ones not...it is no surprise that they grew faster!
In a good comparison you should feed the animals equally to make comparisons. But..I can subscribe that the aquatic animals are a bit more fanatic when it comes to food, so you are easily challenged to give them more as well.

Here is an update one year later. The aquatic group bred last winter, while the terrestrial group did not appear nearly ready. This year, the aquatic group continues to be slightly larger, but only by about 1 cm, on average. The terrestrial group now shows signs of sexual maturity and I will put them into the water this fall.

First, an aquatic female:



Second, one of the terrestrials, obviously a male:

Those guys look fantastic Jen.


I have also found that newts kept terrestrial grow slower than their aquatic counterparts. I've been keeping my T. marmoratus terrestrial and their growth has been incredibly slow, despite ample feedings. Other keepers who have marms from the same clutch have had theirs grow much faster. The difference is that they've been keeping theirs aquatic.

In an attempt to accelerate the growth and development of my marms I've been acclimating them to aquatic conditions, but they're being quite persistant in maintaining their terrestrial status.

i have a group of 6 marms that ive kept terrestrial for close to 2 yrs and they are growing pretty well i must say. they havent grown so much in length as girth. they have grown maybe an inch in length, but have also filled out quite nicely. they are incredibly active and come out from under their log and hunt every time i feed or even spray the cage. they readily eat out of my hand as well. i am troubled with how i should keep my newly acquired N. strauchii however. im torn between aquatic and terrestrial. i kept them terrestrial for the past couple weeks and they seem very inactive and not really eating. so i am trying aquatic now. i just introduced them to about an inch to 2 inches of water on one side and a quarter inch on the other side withplenty of plants. what temps should i keep them at you think?? thanx much! take care

-josh

Hi Josh, regarding temperature, what do you have available? I keep mine in a cool basement. A non-freezing garage in winter is good.

Another person who has the same batch of strauchii juvies has asked me similar questions. If you don't mind, I'm just going to paste in some exerpts from my replies to him. If some of this doesn't make sense, it's a bit out of context...

All the breeders of Neurergus in Europe would tell you that keeping juveniles terrestrial is required. If they seem to prefer that, then it's best. Keep in mind that these guys come from barren rocky habitats. Whether aquatic or terrestrial, you should provide a pile of rocks for them to hide in. Limestone is best, as they come from an alkaline environment. Avoid any acidic substrates, such as peat or other mosses. I use a mix of top soil and coco-fiber with cork bark and/or piles of river rock.

My terrestrial juvies were raised mostly on a diet of live blackworms offered in a dish. The dish needs to have deep sides, and pebbles in the bottom, so that the blackworms don't crawl out and foul the substrate. Also, the dish needs to be checked daily without fail, as sometimes blackworms go rotten fast. I'm attaching a photo of the kind of food dish I have used. It's from Stouffer's Lean Cuisine frozen food.

Once they were big enough (and I think yours are already) I began to add chopped Canadian nightcrawlers into the same wet food dish. The tips of the worms are especially useful, as they continue to wiggle for a long time. The newts seem to prefer to eat at night, or other times when I'm not looking!

The only other foods I've used with them are live crickets and fly larvae (also called maggots or spikes). They love crickets, but personally I wouldn't rely on them too much as a staple, and be sure to dust them with a good vitamin/calcium powder.

Yes, dechlorinated tap water would probably be better. Also, you could probably skip the blackworms, as these newts are fairly large already. Just try putting worm pieces in a water dish (count the pieces) and check later to see if any disappeared. If they reject the Euro nightcrawlers (which sometimes give off a funky odor, some newts won't eat them when chopped), try buying them some Canadian nightcrawlers from a bait shop or walmart.

I would say keep trying with the nightcrawlers, cut up, offered in a shallow water dish. Maybe even withhold any crickets for a few days, then try the worms again. And if you do have an easy source of blackworms, try those, that's what they've been raised on. Feed the crickets some healthy food, and I would dust them maybe every other time.

(Message edited by jennewt on November 01, 2005)

Could we see pictures of your setups?

Josh, I'll do some digging. I'm sure I have photos, but they're somewhat buried. Maybe I'll go take some new ones.

Cool I'd love to see some pictures.
I really love these newts but I know that they're really rare and not good for a begginer at all

(Message edited by twig on November 10, 2005)

*chimes in on seeing Jen's set-ups, including that "lean cuisine" food dish.*

I'm more of a ramen girl, but for the newts, I'll eat some TV dinners.

OK, I did some digging through the archives of bad photographs! Here is a photo of the aquatic setup I used for the "experiment" above. Note, as described above that the animals were first introduced to shallow water, then transferred to this deeper setup.





For the juveniles raised terrestrially, I used this setup:






In this post, I show the aquatic plastic tub setup I'm now using with my current batch of juveniles:
http://www.caudata.org/forum/messages/13/40154.html?1124385466