SNAKES, DEER, BIRD HEADS

[darren.naish@port.ac.uk]

Dann Pigdon wrote about the giant tiger snakes of Chapel Island and 
predatory deer from the Mediterranean. I don't think the tiger snakes 
are a separate species from the mainland tiger (I could be wrong 
though): certainly they are bigger, more robust and far darker than 
their mainland cousins. They are in fact all(?) melanistic, perhaps 
to aid heat absorption in the cooler maritime climate of the island. 
People on the island who collect shearwater chicks go around putting 
their arms deep into the burrows.. the same burrows where the snakes 
are denning. Apparently, burrows with snakes in them are cooler than 
those with chicks in them, the collectors feel this difference 
(yeah right) and thus avoid being bitten.

The deer are not from the Mediterranean, but from the Outer Hebrides 
(IIRC) off Scotland (incidentally they are red deer (_Cervus 
elephus_) and among the few populations in the UK not diluted with 
the genes of feral sika deer (_C. nippon_)). They bite the heads and 
legs off shearwater chicks. Sheep on the islands also eat seabird 
chicks. This behaviour is apparently a consequence of mineral 
deficiency and formed the basis of studies published by Furness in 
1988 (_J. Zool._).

As for ornithischians that may also have been part-time predators, 
stay tuned for some papers currently in the works. There is also much 
interesting stuff about prosauropod omnivory coming out in a volume 
on herbivory in the Tetrapoda, scheduled for this Autumn.

Alan Brush informed us of....
 
> Evolutionary patterns of avian trophic diversification. 1997. by Zweers, 
> et al., in Zoology 100: 25-57
> 
> Evolutionary transitions  in the trophic system of the wader-waterfowl 
> complex 1997 by Zweers and Vanden Berge. in Netherlands J. of 
> Zoology 47 (3): 255-287

I have these papers and they are strange. The authors compare the 
feeding mechanics of various extant bird groups with non-avian 
theropods and find that certain birds are more like certain non-birds 
than others. For example, ornithomimosaurs are most like ratites and 
troodontids like anseriforms (these are off the top of my head so 
don't quote me). What is odd, and confusing, is that the authors 
provide cladograms to depict these trophic similarities, and the 
cladograms make it look like birds are polyphyletic and some evolved 
from ornithomimosaurs, some from troodontids, some from 
dromaeosaurids etc. etc. I don't think this was the author's 
intentions, but it illustrates the perils of using cladograms to 
convey your ideas when what you are expressing is not necessarily a 
graph of synapomorphies or a strict depiction of phylogenetic 
relationships.

Indeed, that cladograms are frequently used as phylograms (e.g., in 
Weish-Dod-Os _The Dinosauria_) has been the bone of some contention.

Darren Naish B. Sc, M. Phil.

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
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