→ simonown:這個帥氣... 推140.112.239.236 01/06
The Dog Family --lobo
Canids originated in North America during the Eocene (54-38 million yrs ago
), 19 genera in the Oligocene (38-26 million yrs ago), 42 in the Miocene (26-7
million yrs ago), declining to the 10 genera recognized today.
Wolves (Red (distinct) and Grey--lobo)
Two species of wolf remain today. The Gray wolf is the largest member of the
dog family. It was once the most widespread mammal, apart from man, outside th
e tropics (the Red fox has that distinction to a few large today). Now it is re
stricted to a few large forests in eastern Europe, some isolated mountain refug
es in the Mediterranean region, mountains and semidesert areas of the Middle Ea
st, and wilderness areas throughout Asia and north America. This decline appear
s to be largely the result of human persecution and habitat destruction. The im
mense former geographic range and ecological adaptability of the wolf are refle
cted in wide variations of form and behavior. The smallest and lightest-colore
d wolves inhabit semidesert areas. Forest-dwelling wolves tend to be of medium
size and grayish. Tundra wolves are among the largest, their coat color ranging
from white through gray to black. Wolves will take a wide range of food. In wi
lderness areas, typical preys are moose, deer and caribou, which weigh up to 10
times as much as a wolf and are hunted by packs. Smaller mammals such as beave
r and hares may be important prey. Wolves will on occasion take carrion and pla
nt material, and even when wild prey is available will scavenge at trash cans a
nd refuse dumps. To find enough food, wolf packs require extensive home ranges,
from 100sq km or less to areas in excess of 1000sq km (40-400sq mi), depending
mainly on prey density. Scent marking and vocalizations (the long, deep ‘mour
nful’ howls that together with yips, barks, growls and whines make up the wolf
vocabulary) help to define and defend these territories. Most packs in foreste
d areas occupy stable, year-round territories. In northern tundra regions, pack
s are usually nomadic as they follow the migrations of caribou and saiga antelo
pe, they may return each year to established summer denning areas.
The nucleus of the wolf pack is the breeding pair (wolves usually mate for
life). Body postures are an important part of the ‘language’ that creates and
reinforces hierarchy in the pack. Pack size depends on the size and availabili
ty of prey. In moose country, pack of up to 20 individuals occur, but this decl
ines to about 7 where the main prey are deer.
There is a pair of wolves
Breeding occurs in late winter and some 4-7 blind and helpless pups are born
in a den. After about a month, the pups emerge, to receive food and attention
from their parents and other pack members. If the food supply is ample, these
‘helpers’ can assist the pups to be fit and large enough to travel with the pac
k at 3-5 months; if food is scarce, their presence may reduce the pups’ chance
s of survival. Some pups leave the pack during the following breeding season, w
hile others remain as ‘helpers’. Wolves are sexually mature at two yrs old.
When food is scarce, there is a pup leaving the pack or they will reduce the pu
ps’ chances of survival.
To Howl or Not to Howl?
How wolves deep their distance
On occasion, wolf packs meet. When they do, a fight may develop, with the commo
n outcome a dead wolf, lying where it fell victim to the other pack, a snarl on
its face as testimony to its violent death.
The likelihood of such disastrous encounters is reduced by each pack restri
cting its movements to a relatively exclusive territory of 65—300sq km (25—11
5sq mi). the territory may be 10-20km (6—12mi) across, but only the outer kilo
meter or so is shared with neighboring packs or lone wolves. How do wolves reco
gnize this periphery and thus avoid it and their neighbors? Scent marking provi
des part of the answer. The dominant animals of each pack urinate on objects or
at conspicuous locations about once every three minutes as the pack travels ab
out its territory. The density of scent marks in the border regions is twice as
high as elsewhere, the reason for which is not fully understood. However, wolv
es are known to increase their rate of scent marking after they encounter scent
marks left by strangers, as they do much more frequently on the occasional vi
sits to the edges of their pack territory. This higher density of scent marks,
both its own and those of strangers, appears to enable a pack to recognize the
periphery and keep from trespassing into even more dangerous areas beyond.
However, scent marks only inform a pack of where its neighbors were, and ap
proximately when they passed through, not about where they are now. If the neig
hboring pack is traveling in the border area along the same trail but in the op
posite direction, then whatever the density of scent marks they alone will not
prevent an accidental meeting. Wolf packs need a more instantaneous spacing mec
hanism, and howling appears to fill this requirement.
When a pack howls, all members usually join the chorus. Under ideal conditi
ons, this chorus can advertise a pack’s location over distances as great as 10
km(6mi). thus a pack can broadcast its whereabouts over much of its territory
in an instant. When two packs are approaching one another along a common border
the chances of hearing howling continue to improve : the more likely an encoun
ter becomes, the better the chance of hearing the neighbor pack’s howling, and
when they do so wolves normally avoid the meeting.
We might expect a pack to howl frequently as it travels about its territory
and to reply immediately upon hearing strangers howl nearby. In fact, howling
occurs only sporadically (in one study, only once every 10 hours), and as often
as not a pack declines to answer a stranger’s howling. The reasons for this a
pparent reluctance lie in another type of encounter between packs. On several o
ccasions, packs in Superior National Forest have been observed to invade a neig
hbor’s territory, follow a trail straight to the residents’ location, and the
n attack them. In at least two of these ‘deliberate’ encounters, resident wol
ves died and, in one case the resident pack apparently disbanded after the atta
ck and its territory was usurped by the intruders. Thus, a reply may incite an
attack.
Although these deliberate encounters are less frequent than accidental ones
, they confront the pack with the dilemma ‘to reply, or not to reply.’ If a p
ack seeks to avoid an encounter, it solves this dilemma by applying a simple ru
le. When the pack can do so with little loss, it usually slips silently away fr
om the strangers. The silence offers no clues to strangers seeking a deliberate
encounter, while any scent marks left by the pack during the retreat can help
to prevent an encounter desired by neither pack. But, if to move off means that
a pack risks losing an important resources for the wolf pack are young pups an
d fresh prey kills : neither can be abandoned without a potentially great loss
to the pack. Packs at fresh kills have replied to neighbors’ howls in more tha
n four out of every five cases observed. The pack’s answering howls prevent an
y accidental meeting, and although they could assist strangers intent to an att
ack the need to defend a valuable resource appears to outweigh the relatively s
mall risk of attack. Older pups, which can retreat with the pack, and already e
xploited kills are not sufficient cause to run this risk ; reply rates of 30 pe
rcent have been observed in these conditions.
This resource-based decision is further modulated by pack size and season.
A pack of 7-10 wolves replied on 67 percent of the nights when the observers ho
wled to them, whereas a pack of 3-5 replied on only 40 percent; and during the
breeding season, when interpack aggression reaches its zenith, reply rates incr
ease for all packs.
There are two other reasons why failing to reply to strangers’ howling may
benefit a pack. If the pack desires to seek out its neighbors, it may be best
to do so unannounced. And because a pack fails to reply about as frequently as
it replies, neighbors are kept uncertain of the pack’s whereabouts, and may re
frain from entering from entering an area despite their howls being unanswered.
A lone wolf keeps a lower profile than a pack. Loners—mostly younger anima
ls that have left their natal pack—travel areas 10-20 times greater than does
a pack. In this search for a place to settle, find a mate and start its own pac
k, the lone wolf rarely scent marks or howls. Many loners never reach their goa
l, but fall victim to hunters, trappers or hostile wolf packs. Once in possessi
on of a vacant area, however, the lone wolf begins to scent mark and will howl
readily in response to strangers, ready to defend its territory.
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 140.112.240.2