Dear friends,
I am posting a digest on the following question I asked to the list a few
days ago.
Thank you very much to all who read and answered it.
Alexandre
ORIGINAL QUESTION
Dear friends,
I am preparing an article about the effects of cattle grazing on the
structure of subtropical riparian forests, and I want to depart from the
ecological foundations of the issue: what kind of predators are cows and what
kind of effects one could expect them to have on forest communities, based on
ecological theory?
Do anyone knows of key references on cattle foraging behaviour regarding
forest seedlings and saplings? Are they specialists or generalists? Do they
impact forest communities more by trampling or by grazing?
I have found mainly descriptive articles on net effects on forest
strucuture, but I am finding it somewhat hard to find the above-mentioned
questions addressed in the ecological literature.
Thanks in advance,
All the best,
Alexandre
ANSWERS I HAVE RECEIVED
* The Konza Prairie LTER in Manhattan, Kansas, USA has done a number of
studies comparing foaging impacts of domestic cattle and buffalo. You might
try to do a search for Konza and buffalo and see what you get;
* A researcher at Texas Tech was modelling the grazing behavior of cattle
back around 1994. I don't recall his name but he was in the department of range
scienes and was applying the disc equation to cattle feeding. Back in my
undergrad days I took some ag classes and recall that in comparing goats,
sheep, cattle, and bison that bison tended to clip grasses and preferred the
fresh grass (in fact native americans would use fire to keep bison in their
area). Cattle tend to prefer forbes, althought they do eat the grasses. Cattle
will pick clean all the forbes out of a pasture over time. They also pull
vegetation rather than clip it, leading to a different kind of grazing pressure
on the vegetation. Sheep tend to pull as well, but also tend to leave much
shorter grazing pastures. Sheep will feed on much "rougher" pasture than
cattle and are better converters of rough forage. Goats tend to be browsers
and will reportedly starve on a grass field if no forbes are present. B!
y no means am I a ruminant biologist, but I think I recall this info
accurately. I recommend you contact the folks at Texas Tech as they will
probably have good info for you. If I remember the Prof's name I will email it
to you, but its been so long! Another good source of information is to look
into some animal science departments or textbooks. There are various papers and
books on ruminant biology, forage management, pasture management, and range
management that might provide you with the information that you are seeking.
* Dear Alexandre, our group works on ruminant foraging behaviour in
(sub)tropical environments. Check our website for articles and staff who might
help you find the information you're looking for. Jasja Dekker, PhD
student, Resource Ecology Group, Dept. Environmental Sciences, Wageningen
University. Bornsesteeg 69 6708 PB Wageningen The Netherlands
http://www.reg.wur.nl/UK/Staff/
* I am currently thinking a lot about classification of consumers in
consumer-resource systems. I work with predator-prey models but have
recently become interested in the larger issue of "what if any discrete
categories of consumers are there?". Cows are tough... by one definition they
are parasites (eat only part of their host), by another they are predators
(larger than their host), by another they are parasitoids (generation time is
about the same as their
hosts [?Maybe?]). Cows are the best example of how little these categories
actually mean.
Dr. Alexandre F. Souza
Programa de Pós-Graduação em Biologia: Diversidade e Manejo da Vida Silvestre
Universidade do Vale do Rio dos Sinos
Av. UNISINOS 950 - C.P. 275
São Leopoldo 93022-000
RS - Brasil
Telefone: (051)3590-8477 ramal 1263
Skype: alexfadigas
[EMAIL PROTECTED]
http://www.unisinos.br/laboratorios/lecopop
