biological diversity and tropical forests in tunisia - PART

Duricg the cesticg season it is conmoc for fishermec to collect eggs
from colocies of Cory's shearwaters acd herricg gulls to supplernect their
dtets. This activity has had a profoccd effect oc the Cory's shearwater
popiilatioc. Ic the past, eggs acd chicks were gathered fron Rleocora's
falcoc cests to supply falconers. Garbage diimpicg, sewage outflows acd
village expacsioc are other hunac icfluecces oc the islac? ecosystems.
Recreatj ocal activj ty also icfluences the fauca of the archjpelago.
For 5-6 mocths of the year, yachts acchor ic the waters of Calite acd
psseccers exgage ic SCUBA divicg acd spear fishing. :Jot ocly does this
activity effect the fish acd coral formatiocs, it also disturbs mock seals
and cesticg birds. Prolocged visits to the shore dcrjcg the cesticg
seasoc cac result ic serio~s losses of eggs dce to icsolatioc.
Feral goats, sheep acd cows are affectjcg the vegetatioc compositioc
acd sxcessiocal stages of Galite. Other jctrodzced mammals are affectire
the facca of the islacds. Rats Rattus norvegicus are foucd on all of the
islets acd comnocly raid the cests of Cory's shearwaters ard g~lls. Rats
are abixdect, or overabzcdact, ever thocgh they are preyed cpx by cats oe
Galite ecd raptors throcghs~t the archipelago. Feral cats elsa prey oc
cesticg birds acd their youcg.
Rabbits are so overabwdact ic some locatiocs that they have taken
over all of the secluded riches where Cory's shearwaters tradjtiocally
cested (~ailthier 1978). Vhec the birds are forced to cse less favorable
locatiocs for cesticg they become miich more vclcerable to cats acd rats.
Rabbits dig bcrrows ic macy of the mwe favorable lacatjocs of the
jslacds. Those djggicgs are sometimes detrimectal to the vegetatjsc,
which is aggravated by the feedicg activjty of the abxdact acjmals.
Galitoc islet was desigcated a strict catcre reserve oc 4 July 1980.
The reserve icclades the islet acd a 0.5 sea mile radjus as ac ictegral
catzre reserve; therefore, jt also iccludes la Fa~chelle islet. Cal5te js
of ictercatiocal importacce because of the ecdacgered Kedjterraceac mock
seals acd the cesting colocjes of A.~douic's gulls, Eleocora's falcocs acd
Cory's shearwaters. Ic spite of the terrestrial acd narjce facra acd
islacd habltat, whjch is at least of natiocal importacce, there is little
active naraeemect at the pressct tine (IUCI~ :987).
3.2.2. Zembra and Zembretta Islands
The Zenbra archjpelago is located ic the C~lf of Tscis rear the
cortherc tip of Cap Boc. At the closest poict, the islacds are 11 kn
corthwest of the maiclacd. Zembra, the largest jslacd of the archipelago,
has ac area of 370 ha. Oc the soctheast sjde of Zenbra is Zenbretta, a
much smaller islacd of 5 ha. There are also two ticy islets - the
Cathedral acd Lactowhe, whjch are cot much more thac rock formatjocs
j~tticg oiit of the sea, 60 m acd 400 m from Zembrs, respectively.
Zenbra 5s e prismatjc shaped moxtajcois islacd ('race 19771, with a
maximcn altit~de of L35 m. There are steep cliffs aroxd the jslacd,
risicg cp to 200 m high oc the corth side, makjcg access difflcclt. At
the bzse of the cljffs acd alocg the rest of thp :2 kn shsrelice there are