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marblenewt
1st March 2016, 19:11
Hello everyone.

With this thread I would like to expose an incident, of so far unknown origins, which took place (and might be ongoing) in a specific region and has apparently culled the population of the adult species in question. I initially contacted European individuals in attempting to obtain some help on what was causing not just so many deaths, but deaths in a strange fashion - to amphibian enthusiast or not.

The little information that I sent turned out to provide little context, and, without this, some speculation was working on unlikely situations and wrong assumptions. In a attempt to remedy this, I produced a small report going over the necessary details I imagined are needed for someone attempting to think of the problem from a distance.

There is ongoing discussion (in Italian) at Forum Natura Mediterraneo, on this thread (http://www.naturamediterraneo.com/forum/topic.asp?TOPIC_ID=265416), which has been reacting to the content in the document provided here. I hope that here the same can take place in English.

In creating this thread, I am starting a discussion for those who can point out the reasons for this mortality, so that I won't actively participate unless specific questions need to be addressed regarding my experience with the event.

That said, the pdf document exposing the situation can be downloaded here (https://drive.google.com/file/d/0B37K_G9FbxeyZG10VjBhend0Wms/view?usp=sharing), through Google Drive. I have assumed it pedantic to repeat any of its content in this thread.

Thank you.

garfield188
1st March 2016, 20:53
Could it be the newt killing fungus Batrachochytrium salamandrivorans?

schmiggle
2nd March 2016, 00:40
This is very sad. I hope the problem is solved soon. My gut reaction was that it was human caused, but perhaps that is unsupported by evidence (I can't read Italian, so maybe that was discussed on the forum linked to by the OP).
Bsal does not cause newts to become eviscerated, as these were. They just get massive lesions and die.

Chinadog
2nd March 2016, 08:23
Welcome to the site marblenewt. :)
I've moved this thread to the ecology section as the topic may well involve other wildlife.
I remember seeing a TV programme about the mutilated Bufo toads, I think it may have been Animal X on the BBC, it will be very interesting to see if this case is similar.

marblenewt
14th March 2016, 19:32
Hello everyone.

I have news regarding the case of the newts. It turns out that very similar depredation has been documented in the last decade, and the principal culprit might be a surprise; the otter (Lutra lutra). The otter, perhaps along with other mustelids, seems to be quite capable of manipulating amphibian prey and being very particular as to what it consumes. While newt depredation is more or less newer, that regarding toads is decades old; part of the type of prey handling exhibited by otters on toads has been termed progressive skinning and skinning behaviour. A documented instance of depredation on Pleurodeles waltl by otters fits the type of ventral cuts visible in the bodies of the Triturus marmoratus I photographed. For the moment, it has been difficult to ascertain how and why an otter would travel to the area to consume marbled newts specifically, which has opened consideration for two other mustelids; Mustela putorius and Neovison vison. The latter considered more credible and likely due to its diving capability. Scavengers that might have caused (extra) mutilation, such as Corvus corone, have not been excluded for that role.

For those interested, here's some relevant literature:

For the best example (so far), in terms of similarity, of depredation of newts by otters see Impact of otter (Lutra lutra) predation on amphibians in temporary ponds in Southern Spain

For the otter as toad predator see PROGRESSIVE SKINNING OF TOADS (Bufo bufo) BY THE EURASIAN OTTER (Lutra lutra) and Seasonal use of ponds as foraging habitat by Eurasian otter with description of an alternative handling technique for common toad predation

For generalized newt predation by otters see Predation of newts (Salamandridae, Pleurodelinae) by Eurasian otters Lutra lutra (Linnaeus)


Thanks.

Chinadog
14th March 2016, 20:59
Fascinating subject, thank you for posting!

xxianxx
14th March 2016, 22:31
Interesting articles, I have seen hundreds of degloved frogs and toads over the years at my local reservoir and always thought the likely culprits were foxes and mink. Havent seen any otters or otter scat there and I am familiar with seeing both having fished the wye since childhoood, the very occasional one passing passing through has been reported a hand full of times in twenty years but they certinly dont form a permanant or seasonal population.The predation reported by the op could have another species or series of species involved. Will definitely be doing some further reading and follow this thread.

xxianxx
14th March 2016, 23:28
Alien mink predation induces prolonged declines in archipelago amphibians | Proceedings of the Royal Society of London B: Biological Sciences (http://rspb.royalsocietypublishing.org/content/273/1591/1261)
Looks like feral mink are not the culprit for the toads I have seen degloved, if I can find the same info for foxes I'm off otter spotting lol

JM29
15th March 2016, 10:13
Ironically, the general improvement of water quality in my area do favors re-colonization of rivers and body waters by the otter.
Amphibians will have to face another problem.