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"SHREW TALK" - Vol. 1, No. 07 - 1 July 1997

SHREW TALK - 1 July 1997 - Vol. 1, No. 7
Number of Recipients: >180
Contents of this Issue
o Editorial
o Research
1. Shrews and frogs
2. Shrews, frogs, and salamanders
3. RE: Shrews and frogs: a summary
4. Salamanders and shrews
o What's New on the Shrew (ist's) Site?
o Shrew (ist's) Site - Related Inquiries
o Shrew Talk Instructions
Dear Shrew-Fessionals and Shrew-Mateurs,
In this issue we cross the border to herpetological realms. Dr. Windmiller's message is closely connected to an inquiry by myself in 1996 that is still of immediate interest. It therefore seemed necessary to quote this and some replies I received at that time as well, in order to provide the context.
Please pass this newsletter on to any of your colleagues involved in herpetology or feel free to disribute it among the herpetology newsgroups.
Your's shrewly,
Werner Haberl
Shrews and frogs:
In the past years we have found several locations at Austria's Lake Neusiedl with depots of killed and partially eaten frogs (Rana lessonae / esculenta). We would like to know about the predators.
I know that the European water shrew (Neomys fodiens) kills, stores and eats frogs. But I also know that this behaviour is typical for Mustela putorius. We are uncertain about the predator. The signs, according to the eating patterns (sometimes very fine: small, juvenile frogs skeleted at the hind or forelimbs and/ or eyes eaten) suggest that it must have been a small predator like a shrew. Other circumstances (the great number of killed frogs, the large body size of some frogs and the literature referring to Mustelidae) still confuses us. Killing frogs and only eating the liver is also reported from Rallus aquaticus (Aves). Besides, we are aware that the predator catching and caching the frogs may not be identical with the animal eating the carcasses. We want to find out more by some fieldwork (trapping) next year, but I would be grateful if anybody could supply us with some information on this topic.
The hypotheses are:
a) Frogs were caught, cached and eaten on by shrews (this would comply with earlier findings described in the literature and my personal observations in captive shrews)
b) Frogs were caught, cached and eaten on by a larger predator, eg Mustela putorius.
c) Frogs were caught and cached by a larger predator, eg Mustela putorius and then utilized by a small mammal, eg a shrew.
The complications in finding scientific evidence for either of the hypotheses lie in i) the only occasional occurence of the phenomenon, ii) the difficulty of direct observation and iii) that the area where these depots were found is within the boundaries of the National Park and thus extensive field studies are restricted.
Regarding the (below) contribution by Dr. Delfino, I would like to know if there is anybody that has experience in discriminating minute tooth marks on bones or skin or has any samples that can be used for a comparison.
The literature I have found on this topic should be fairly complete as it concerns shrews. The list can be found on The Shrew Site at: http://members.vienna.at/shrew/bibselections3.html but I would appreciate it, if anybody could provide further references or leads.
Thank you in advance, Werner Haberl - shrewbib@sorex.vienna.at _______________________________________________________________________
Date: Sat, 28 Jun 97 15:07:17 UT
From: "Bryan Windmiller" <bwindmiller@msn.com>
Subject: Shrews, Frogs and Salamanders
Dear Werner et al.,
Thanks for your response to my subscription. I am a Ph.D. herpetologist, having completed my dissertation on Ambystoma habitat preferences at Tufts University, Massachusetts, USA last year. I now work as a self-employed ecological consultant, mailing address:
Bryan Windmiller Hyla Ecological Services 65 Arrowhead Road Concord, MA 01742 USA
I was intrigued by your observation of caches of killed / partially eaten Rana lessonae in Austria. Through drift fence / pitfall trapping I've had plenty of opportunity to witness the effects of Blarina and Sorex cinereus predation on amphibians and the injuries that you describe (chewed or skeletonized limbs, missing eyes) were common amongst the unfortunate amphibians that shared my pitfalls with shrews.
My own interest in shrews was particularly spurred by the following observeations:
a) I radio-tracked adult Ambystoma maculatum and found that they almost always inhabited small mammals burrows. Since I knew, from pitfall trapping, that Blarina brevicauda was the most common small fossorial mammal in the area, I kept a few in "ant farm" type enclosures and found that the burrow systems that they excavated were similar in diameter and general pattern to those inhabited by the salamanders.
b) Adult A. maculatum that spent the night in a pitfall with Blarina were never visibly injured, implying that their toxicity and ability to wave and spray their toxic glandular secretions in the face of a potential predator were sufficient to dissuade even starving Blarina from further attacks. However, newly-metamorphosed spotted salamanders were often killed by Blarina in the pitfall traps but the shrews would only eat the limbs and head leaving the dorsum and tail (where the densest arrays of skin glands occur) intact. Perhaps this is why newly-metamorphosed A. maculatum are found under logs but not within small mammal burrows far more often than adults - it may take some time and the attainment of a critical size or density of toxin-secreting skin glands for them to effectively repel Blarina and thus dare to enter the shrews tunnels.
I haven't studied this relationship any further and am particularly interesting in first ascertaining whether adult Ambystoma and Blarina actually use the same burrow system simultaneously. Does anyone have observations that would support this conclusion?? Thanks.
Bryan Windmiller _______________________________________________________________________
RE: Shrews and frogs: a summary
From: tulse@eponet.it
Date: Sun, 15 Dec 1996 14:52:10 +0100
Subject: Re: frogs & shrews
As a paleoherpetologist I am involved in the problem. There are several taphonomic problems involving the assemblages of frogs' bones and it would be interesting for me to know exactly the predator. If tooth marks are present on the bone surface it's possible to discriminate between Rodents or Carnivores. This kind of difference is generally observed with S.E.M. (Scanning Electron Microscopy).
I would suggest you to go deeper in the problem and collect the remains for a S.E.M. study.
I'll wait for a study concerning taxa and numbers of predators, taxa and numbers of prey, depot typology, presence of tooth marks on the bone surface, .... Please keep me informed.
Kindest regards,
Massimo Delfino
Vertebrate Paleontology Laboratory Earth Science Department
University of Florence Florence ITALY
From: SR71BLBRD@aol.com
Date: Sat, 30 Nov 1996 20:15:39 -0500
Subject: RE: Subject: Frogs & Shrews
Rana pipiens -- Northern leopard frog & Blarina brevicauda -- Shorttail shrew
The local Shorttail shrews do eat chunks from the frogs, maiming or killing the frogs. Overnight, on the first two mornings of the frog migration, and on a few later occasions, some or most of the frogs in the window well pit-trap would have suffered one injury somewhere on their body - a bitten leg or foot, a missing leg, a bite take from the nose, missing eye, a hole in the ribcage, etc. The injured frogs, those still alive, would be likely to squeal before being picked up, although throughout the season, many would squeak, as well as cower, before being handled. Twice in the past year, in my basement, I have accidently trapped up to three Shorttail shrews at a time within live mouse traps. ( ... to the great detriment of the mice within the trap.) Thus I am sure that the Shorttail shrew is also the species inflicting the wounds on the frogs.
David Hoag, 173 West Shore Rd., Grand Isle, VT 05458, USA
Date: Thu, 28 Nov 1996 09:00:55 +0100
From: airoldi@kl.unibe.ch (J.P. Airoldi)
Subject: killed frogs
Back in 1970, we also observed frogs (Rana temporaria) killed along a creek which they have to cross in order to go from the woods to a nearby pond to lay eggs. We were puzzled by the fact that some frogs were just killed, but no eaten; others had parts eaten, like legs, or head, or flanks. We concluded it was Rattus norvegicus after we found tracks corresponding to that species. In many places we leveled the surface and put some fine sand and clay so the tracks would be well visible. This killing happened many years in a row, always in Spring when the frogs went to the ponds for egg-laying. I do not know whether frogs are still killed in that area. Nobody to my knowledge has continued to look at it recently.
Best regards, Jean-Pierre
Dr. Airoldi Jean-Pierre
BES / Biologie Université de Berne
Gertrud Wokerstr. 5 CH - 3012 BERN (Switzerland)
Tél. + 41 31 631 45 71 FAX + 41 31 631 85 40
e-mail: airoldi@kl.unibe.ch
Date: Fri, 29 Nov 1996 13:42:17 +0100
From: <J.Wilkinson@open.ac.uk>
Subject: Re: Shrews and frogs
There are several observations of herons voiding large numbers of part-digested frogs after a feeding frenzy, they have apparently overdosed on their skin toxins, and "caches" or piles of dead frogs (and newts) have been seen on the shores of large UK lakes. These have also been usually attributed to herons. It sounds as if your findings could not be explained purely by this phenomenon, however, but maybe they account for a few incidences?
I would be very interested to know if you discover more about these phenomena. By the way, I am an amphibian ecologist, currently working for the DAPTF at the Open University.
With very best wishes, John W. Wilkinson,
International Coordinator, Declining Amphibian Populations Task Force.
PRIVATE E-MAIL: j.wilkinson@open.ac.uk
DAPTF: DAPTF@open.ac.uk
WWW: http://acs-info.open.ac.uk/info/newsletters/FROGLOG.html
Date: Thu, 19 Dec 1996 11:59:17 +0100 (MET)
From: "Henk Strijbosch" <hstrijbo@sci.kun.nl>
Subject: Frog predation
With some intervals I am working with amphibians for more than 25 years in the Netherlands.
The depots of killed frogs (or toads!) you describe are found by us frequently. Just like you we mostly are not sure about the real predator responsible for the killing and responsible for the eating. We have found traces of Mustela putorius and of Rattus norvegicus on the 'killing fields', but we never could determine the predator with absolute certainty. Yet we are sure, that the victims are (partly) eaten by more than the killer itself. So the fine eating patterns found by you can be caused by another predator than the killer.
Henk Strijbosch _______________________________________________________________________
Date: Wed, 05 Mar 1997 15:25:44 -0500 (EST)
From: Wayne Van Devender <vandevenderr@appstate.edu>
Subject: Salamanders and shrews
(message shortened by WH)
(Ron Nussbaum offered to let Butch Brodie use one of his Dicamptodons in a threat display presentation with Blarina. The outcome was well known to Nussbaum in advance, since he had read the literature. The salamander instantly ate the shrew!) (...)
Dicamptodon is a large predaceous salamander long known to eat mice and shrews.
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