Hysl i ,
(n.s.)
3
(1991): 199
-
214
A i
I
Simp. I d. Ca ni o i
METHODS
OF
CENSUSING RED FOX
(VULPES VULPES)
POPULATIONS
METODI
DI
CENSIMENTO
DELLA VOLPE
(VULPES
WLPES)
JUAN
F
RAN
C
I
S
C
O
BELT-
(*),
MIGUEL
DELIBES
(*)
&
JAIMP,
R.
RAW
(**)
ABSTRACT
Es ima ing absolu e
o
ela i e numbe s in ed
ox
popula ions is no an easy ask. Al hough a
ange
o
me hods has been desc ibed, nei he
an
op inid no a uni e sally accep ed echnique has
been ound. Mo eo e , none has been es ed on popula ions
o
known size. We e iewed
he
e iciency
o
ou een indices o
ox
abundance classi ied in o wo g oups:
(a)
me hods whe e
indi iduals a e cap u ed and ma ked, which include ea agging o simila conspicuous ma kings, oe
clipping, adioac i e agging o aeces, adio- acking, and s a is ics om hun ing and apping;
(b)
me hods no equi ing cap u e, which include bo h di ec me hods (noc u nal coun s, unsys ema ic
obse a ions, and d i e censuses), and indi ec me hods (den coun s, ansec s o ack, sca coun s,
and scen s a ions).
As
a ule, s a is ics a e a ely applicable o popula ions es ima es. Me hods
in ol ing cap u e a e expensi e bu p o ide mo e accu a e es ima es han he second g oup
o
indices,
which a e
no
sui able o pai ed compa isons om one yea o ano he . Managemen and
wildli e specialis s should ha e in mind such es ic ions when conside ing
hei
goals and he
equi ed le el o accu acy. Fmally, we ecommend
he
simul aneous u iliza ion and compa ison
o
se e al me hods (one om each g oup, as p oposed
in
a double sampling s a egy)
o
op imum
e alua ions.
Key wo ds: Census me hods,
Vulpes
ulpes,
Canidae.
RIASSUNTO
La
alu azione della consis enza di una popolazione di Volpe, median e censimen i assolu i
o
ela i i,
b
di di icile soluzione. T a i di e si me odi di con eggio impiega i, nessuno si
è
i ela o
o imale
e
uni e sale. Tu a ia nessuno
è
s a o ulilizza o pe popolazioni
di
consis enza no a. Qui
esaminiamo la alidi à
di
14
me odi impiega i pe
il
calcolo di indici di abbondanza, ipa endoli in
due g uppi: (a) me odi che implicano la ca u a e
il
ma camen o degli animali median e ma che
au icola i
o
con assegni simila i, ampu azione delle alangi, adioiso opi ile abili nelle eci, colla i
adio eleme ici e me odi che
si
basano sulle s a is iche ena o ie e sui appolaggi; (b) me odi che
non ichiedono la ca u a degli animali e che igua dano sia ile amen i di e i (con eggio no u no,
awk amen i casuali, censimen o in ba u a), sia indi e i (con eggio delle ane, con eggio delle
imp on e e delle eci
su
pe co si dc ini i, s azioni odo i e e). Ra amen e l'analisi s a is ica
è
applicabile alle s ime della consis enza delle popolazioni.
I
me odi che implicano la ca u a degli
animali
sono
mol o impegna i i
in
e mini di empo
e
cos i, ma o niscono s ime più accu a e ispe o
a quelli del secondo g uppo che non sono ada i pe la compa azione dei da i da un anno all'al o.
Ques i limi i anno a en amen e conside a i in elazione aiie inali à e
ai
g ado di p ecisione che si
in ende aggiunge e. Noi sugge iamo l'impiego simul aneo di più me odi
di
censimen o
(almcno
uno
pe ciascun g uppo), pe una compa azione inc ocia a dci da i e pe o ene e una s ima co e a
della consis enza.
Pa ole chia e: Me odi di censimen o,
Kdpes
ulpes,
Canidae.
(*)
Es aci6n Biolbgica de Doiiina,
CSIC.
Apdo.
1056.
E
-
41080
Se illa, Spain
(**)
Dp o. Ciencias Exac as
y
Na u alcs,
IPO,
Casilla
933,
Oso no,
Chile
I
NTRODUCTION
We will use he e m census in a b oad sense. Censuses a e commonly aimed
no
so
much a de e mining he ac ual numbe s o indi iduals in a popula ion
(O e on, 1971; Da is and Wins ead,
1980),
bu a he a es ima ing an index
o
abundance om a ce ain sampling size. This allows he compa ison o a eas on a
empo al and/o spa ial basis. In any case he p oposed a ge is no easily
achie able and i
is
expensi e.
No
one
me hod, among he many desc ibed in he
li e a u e, can
be
conside ed as he bes
o
he one always yielding op imal esul s.
Ail
o
hem ha e limi a ions and mos
o
he assump ions
upon
which sampling
p ocedu es a e based a e no usually me (Rau, 1988; Es es and Jameson, 1988).
Mo eo e , he e
is
ha dly a simple case whe e indexes ha e been compa ed using
popula ions
o
known
size
(e.g. Da is and Wins ead,
1980).
Two o he aspec s
o
censusing me hods dese e mo e a en ion han hey a e
commonly gi en. Fi s ly, he le el
o
accu acy (i.e. esolu ion) gi en
by
censusing
is
o en below accep able limi s. Rolley (1987) s udying his subjec in bobca s
(Lym
u us)
-
a medium sized ca ni o e
-
s a ed ha
no
single echnique has
p o en sensi i e enough o de ec ing changes smalle han
10
-
25%
wi hin a
popula ion.
Thus,
he e ec
o
any
ac o po en ially egula ing he popula ion
could no likely
be
de ec ed unless i would exceed his pe cen age. Secondly, he
ela ionship be ween cos o censusing and esul s ob ained is o en dis ega ded by
he esea che . Usually, he mos amilia me hod has he highes p obabili y
o
being chosen. Specialis s in e es ed in es ima ing Red
ox
abundance a a gi en
Tab.
1
-
Summa y
o
me hods e iewed in his pape
o
es ima ing popula ion size in
K ipes
ulpes.
~~ ~ ~~~
A.
-
METHODS REQUIRING CAPTURE
A.l.
-
Cap u e
-
ma k
-
ecap u e me hods (CMR)
i.
-
Conspicuous agging (ea
-
agging, colla ing e c.)
2.
-
Toe
-
clipping
3.
-
Radioac i e ma king
o
aeccs
A.2.
-
Home
ange
size
A.3.
-
S a is ics
5.
-
Hun ing Indica o o Popula ion Densi y
(HIPD)
6.
-
T ap
-
lines
B.
-
METHODS
WITHOUT
CAPTURE
€3.1.
-
Di ec me hods
7.
-
Nigh coun s
8.
-
D i e
census
9.
-
Non
-
sys ema ic obse a ions (sigh ings)
10.
-
Den
coun s
11.
-
T ack coun s
12.
-
Sca coun s
13.
-
Scen
-
s a ion ines
14.
-
O he
(
"
a
pos e io i
"
)
B.2.
-
indi ec me hods
200
place and ime need o know, a leas c udely, bo h he inpu equi ed and esul s
ob ainable om he a ailable me hods. Only in his way one can choose he mos
sui able me hod ascomp omise be ween his needs (i.e. goals, aims) and his
esou ce a ailabili y (i.e. money, helpe s, e c.).
This
pape is aimed a e ising ou een di e en me hods ha ha e been used
o es ima ing Red ox popula ions ei he by
us
a he Do iana Biological Rese e
(DBR)
(Rau e al., 1985a), o by o he au ho s in o he coun ies. We include
me hods applied o o he ca ni o es which can be adap ed o ox census, and we
ou line he p incipal ad an ages and limi a ions
o
each.
M
ETHODS
REQUIRING
CAPTURE
F om a p ac ical pe spec i e, me hods o es ima ing Red ox popula ions can be
classi ied
in o
hose ha equi e he cap u e o
indi iduals
and hose ha do no
(Tab.
1).
Among he
i s
g oup, he e a e
ob ious
di e ences
i
he esea che
himsel cap u es he animals and eleases hem a e wa ds (cap u e-ma k- ecap u e
modi ied),
o
i da a a e ob ained om cap u es ca ied ou wi h a wide ange o
echniques (e.g. hun ing and apping).
CAF'TURE-MARK-RECAPTURE METHODS (CMR)
Because
i
allows
many
possibili ies, his me hodology has been gi en a lo o
a en ion in he li e a u e (e.g. O is e
al.,
1978; Sebe , 1982; Whi e e al., 1982;
Mon gome y,
1987).
Ne e heless, oxes a e di icul o cap u e and e en mo e o
ecap u e,
so
ha his me hod canno be s ic ly applied. Ins ead, oxes should be
cap u ed and ma ked wi h di e en sys ems, which allow o iden i y o de ec
hem
om
a dis ance (S onehouse, 1978). The heo e ical basis
o
CMR
me hods has a
simple o mula ion:
in
a
popula ion o N indi iduals,
M
indi iduals a e cap u ed
and ma ked; om a subsequen sample
o
'In''
indi iduals o he same popula ion,
"me'
ma ked indi iduals a e ound. The size o he popula ion is hen gi en
by:
N
=
(M.n)/m
The p incipal assump ions a e: a) he popula ion
is
closed (Lincoln
-
Pe e sen
o
Schnabel p ocedu es can hen be applied, e.g. Todd e al., 1982, hough es ima o s
o open popula ions such as hose o Bailey, and Jolly-Sebe a e also a ailable,
e.g. Cla k, 1972; Caughley,
1977);
b) indi iduals a e equally ca chable, ha
is,
he
sample
is
homogeneously dis ibu ed among he popula ion,
bo h
be o e
cap u ing
and a e ma king. The socio
-
spa ial o ganiza ion o oxes
-
as
o o he ca ni o es
-
in alida es he second assump ion, and co ec ion ac o s a e necessa y (Bu nham
and O e on, 1979; Pollock, 1982; Pollock e al., 1985, among o he s).
An
addi ional p oblem conce ning his me hodology is he di icul y o es ima ing he
cap u e a ea, since he ange o mo emen s o indi iduals
is
o en
unknown.
Radio
-
acking can usually sol e his p oblem (G eenwood e al., 1985; Ku eld e
al.,
1987;
Babb and Kennedy, 1989).
201
CMR me hods yield absolu e es ima es o densi y (numbe indi iduals/ a ea).
As
a ule, any censusing me hod could yield an es ima e o he whole popula ion,
hough i seems mo e app op ia e
-
see below ansec me hods
-
o
conside
census esul s only as ela i e abundance es ima es (Kolb, 1982; Ebe ha d and
Simmons, 1987).
CMR
me hods
a e
po en ially use ul o sampling oxes i he unde lying
assump ions can be me .
CONSPICUOUS
TAGGING
Colou ed ags and o he ma ks ha a e di icul o see a nigh a e no sui able
o he Red ox, gi en i s noc u nal o c epuscula ac i i y. Howe e , e lec ing
ma ks (Macdonald, 1987) which can be li up om a dis ance, can be a e y use ul
aid. This me hod equi es open places equen ed by oxes and he possibili y o
a esea che o co e as la ge an a ea
as
possible.
A
DO iand Biological Rese e,
a
7,000
hec a es s udy a ea in he Do iana Na ional Pa k, Sou hwes e n Spain,
we
ma ked oxes wi h adio- ansmi e s i ed
o
e lec ing colla s (Deiibes a id
Bel an, 1986), bu he sca ci y
o
obse a ions (see below Sigh ings) due
o
hick
sh ubs made his me hod unusable. O he au ho s ha e ea - agged oxes, bu
unless a co ec ion is made o ag losses, his me hod may gi e e oneous esul s
(Hu be e
al.,
1976; Englund, 1980).
TOE
-
CLIPPING
Wildli e specialis s ha e used con olled inge ampu a ions
in
coyo es
(Canis
Zu um)
in o de o ecognize hei acks (Andel ,
1981;
Henshaw, 1981). The
popula ion can
be
es ima ed ai ly accu a ely om he a io o
"
no mal
"
o
"
ampu a ed
"
animal acks, bu his me hod is es ic ed o places and
ci cums ances whe e acks can easily be de ec ed (snow o sand ansec s, di
oads, e c.).
A
su gical ope a ion may also be conside ed une hical
on
c uel y
g ounds and because he animal
is
le wi h a pe manen handicap.
I
has he
ad an age ha se e al popula ion ca ego ies can be ma ked (by sex, by age,
indi idually, e c.), acco ding o he numbe and posi ion o he ampu a ed inge s,
which allows mo e eliable and s uc u ed es ima ions.
RADIOACTIVE
MARKING
OF
FAECES
Ma king o aeces wi h adioac i e iso opes has been in use o some wen y
yea s o es ima e popula ion size in qui e a numbe o species. I was i s
employed o census ox popula ions (Nellis e al., 1967) and hen o he ca ni o es,
wi h success (Conne and Labisky, 1985; C ab ee e al., 1985). Once cap u ed,
animals a e gi en an in amuscula o in ape i oneal injec ion
(5-100
mic ocu ies)
o
one o se e al combined adioac i e iso opes,
usually
Zd5
and
Cdl@,
bu
also
Ce1@, Co n and Mn'54. Iso opes a e chosen o hei low adio
-
oxici y
(mos o hem emi gamma adia ions), a mean physical and biological li e adjus ed
o s udy pe iod ( anging om some weeks o yea s), and he majo ou e
o
elimina ion o he iso opes h ough aeces, among o he cha ac e is ics (Pel on and
Ma cum, 1977; K uuk e al., 1980). I i e o he abo e ci ed iso opes we e injec ed
singly o in combina ion wi h any o he , up o
15
di e en indi iduals o coho s
o a wild popula ion could be ma ked, making i possible o ca y ou simul aneous
sampling o in apopula ion di e ences
in
habi a
use,
ood p e e ences, ma king
beha iou , e c. (Sibly and Smi h; 1985).
A
majo obs acle
o
his echnique, besides he co ec iden i ica ion o sca s, is
he way e i o y enu e sys ems by di e en indi iduals can in luence de ec abili y
o
aeces.
Fo
ins ance, a e i o ial ox may use mo e conspicuous places o ma k
han a ansien one; males may ma k in di e en places han emales and mo e
equen ly, e c. Once mo e, adio- acking would be an ideal complemen a y ool
(Mi chell-Jones e al., 1984; Conne and Labisky, 1985). Conside ing i s
ad an ages, adioac i e ma king o aeces p o ides a e y good app oach o
mee ing
he
assump ions o CMR me hodology because
o :
a) he s a is ical
independence
o
he ma king and ecap u ing phases
o
he echnique,
b)
he
ela i ely small selec i i y in ecap u e (i.e. low deg ee o he e ogenei y), and
c)
he ela i ely high ecap u e p obabili y,
HOME
RANGE
SIZE
This
is
p obably he mos common me hod applied o ca ni o e s udies, Ou
knowledge o hese elusi e mammals has d ama ically inc eased wi h he
de elopmen
o
adio- eleme y de ices (Pa ic e al., 1982; Kenwa d, 1987).
Densi y es ima es
(D)
a e ob ained om he equa ion:
whe e
H
is he mean indi idual home ange size popula ion, which can be
e alua ed by a ious algo i hms (S uwe and Blohowiak, 1989).
This me hod es ima es mhimum yield alues (i.e. i unde es ima es
he
popula ion), because i is assumed ha each home ange is used exclusi ely by one
animai. This is no always ue. Foxes li e
in
social g oups whose sizes a y in
ela ion
o
he abundance and spa ial dis ibu ion
o
esou ces (Voig and
Macdonaid, 1984; Doncas e and Macdonald, 1991). Thus, es ima es based on his
me hod mus be ea ed wi h cau ion, pa icula ly when sample biases a e
suspec ed (Laund é and Kelle , 1984).
In
ou s udy a ea, Red oxes we e adio acked and sampled wi h o he census
me hods a he same ime in o de o e alua e and imp o e di e en echniques.
Besides he di icul y no ed abo e, we ound ha his me hod could be misleading
because he seasonal a ia ions obse ed in home ange size we e no associa ed
wi h changes in absolu e densi y (Rau, 1988).
D
=
1/H
HUNTJNG
AND
TRAPPING
LINES
The numbe o oxes hun ed du ing spo , managemen
o
boun y ials o e a
whole coun y, s a e, e c. p o ides su icien in o ma ion
o
es ima e
HIPD
203

abundance index (Hun ing Indica o o Popula ion Densi y, Zimen, 1980). The
HIPD
o
simila indices show a high deg ee o eliabili y o de e niining
popula ion ends o e la ge a eas. Voig (1987) (see also Kolb and Hewson, 1980;
Kolb, 1982) has poin ed ou ha moni o ing o hun ing
o
apping cap u es is
likely o p o ide he bes es ima es
o
empo al a ia ion in he popula ion when
he da a come om la ge enough a eas, despi e some non
-
negligible p oblems (see
Smi h e al., 1984). P obably one o he mos signi ican handicaps is in he way
how hun ing and apping da a a e collec ed, being coun y dependen .
A
good
idea o he quali y o in o ma ion po en ially ob ainable is o be ound
in
he u
sales ables o No ak e al. (1987). O he no able s udies a e desc ibed in Jenkins
e
al. (1981), and
he
classic pape by El on and Nicholson (1942).
Zimen (1980) eco ded a close associa ion be ween empo al e olu ion
o
he
HIPD and abundance o abid oxes in he samples.
An
index could hus be
cons uc ed
a
pos e io i (see below) wi h adequa e adjus men s, o p edic ox
popula ion ends om he abid oxes hun ed.
We ema k,
as
a conclusion o his second ca ego y
o
me hods equi ing
cap u e o animals, he ela i ely low cos in ol ed i sui able da a (i.e. su ey plans
and egis a ion) a e collec ed, and he high eliabili y o hese me hods, al hough
some co ec ion ac o s (e.g. cap u e pe uni e o when hun ing e iciency, u
p ice, and o he a iables a ec he sample), mus be conside ed o in e p e ing
he da a.
M
E
T
H
O
D
S
WITHOUT CAPTURE
NIGHT
COUNTS
The p o ocol
o
his me hod can
be
summa ized as
ollows:
using
a
ehicle
equipped wi h a mo eable spo ligh , a leas wo pe sons make
a
ansec su ey
(40 km in A ois, 1981)
a
a cons an speed (10
kmhou ),
wi h eplica ions
(2
-
5)
o he ansec
on
consecu i e nigh s.
The me hod was i s designed o census lagomo ph popula ions, la e being
applied o ca ni o es in open habi a s (Wase , 1980). A ois (1981), and Schan z
and Libe g (1982),
among
o he s (see also Pandol i e al., 1991), ha e success ully
adap ed he me hod
o
es ima e ed ox popula ions. Lloyd (1980) desc ibed how
his me hod could be used in o es ed a eas well in e sec ed by oads:
"ln
such
places oxes in ields adjoining oads a e no dis u bed by passing ca s and
sigh ings can
be
made a ixed in e als along he oadside
...'I.
Ne e heless, se e al ac o s should be aken in o accoun
€o
a s anda dized
me hod. Fo example, A ois (1981) ound he mos a ou able condi ions o
census we e be ween 21.00
-
03.00
a he newmoon, wi h high cloud co e , and no
wind. O he ac o s he conside ed we e he annual cycle o ege a i e co e and
he s uc u e o he ox popula ion.
An
au umn census could be used o de ec he
inc ease in
ox
numbe s due
o
ec ui men and dispe sal, while
an
ea ly sp ing
es ima e would comp ise la gely b eeding indi iduals.
204
Nigh coun s can be con e ed o es ima es o absolu e densi y i : a) he ange
o isibili y
is
es ed each ime, and b) plo s o a known a ea a e sampled ins ead
o a ansec line (Schan z and Libe g, 1982). Time
uni s
( oxes coun edll-iou ) a e
p e e able o compa ing a eas ha di e
in
habi a composi ion. Ano he
a ia ion
on
he p ocedu e is o pa i ion a line ansec in o habi a segmen s. This
op ion could also imp o e possibili ies o da a analysis.
As
o any line ansec p ocedu e (Bu nham e al., 1980), a basic ule is o
s anda dize he sou ces o a ia ion associa ed wi h sampling e o (some
men ioned abo e, also he expe ience o s a , abo e all i nigh coun s a e
pe o med o se e al species simul aneously, e.g. p eda o s and p ey). Clea ly, one
o
he mos signi ican p oblems wi h nigh coun s is he g ea a ie y o ac o s
in luencing he use o space and ime by animals. Fo example, one could ask:
Wha pe cen age
o
he
ox
popula ion is eally coun ed, (i.e. de ec able) by
spo ligh ing?
A
sui able co ec ion ac o has been calcula ed by adio
-
acking ed
oxes and de e mining he mean pe cen age
o
ime spen by se e al indi iduals in
open habi a s, whe e hey we e de ec able by spo ligh ing (Schan z and Libe g,
1982).
DRIVE
CENSUS
The animals a e d i en in o a delimi ed a ea by ained people, some imes
assis ed by hounds, and coun ed as hey c oss he obse e ’s line. O e on (1971)
ci ed
a
simpli ied e sion
o
his me hod by eplacing he obse e ’s line wi h a
sand ansec
(o
o he so ma e ial) om which he animal acks could la e be
iden i ied.
This
me hod can be used success ully
in
woodland o dense ege a ion co e ,
such Medi e anean sh ubland. Fo example, Telle ia and SAez-Royuela (1984)
es ima ed densi ies o ox and oe dee
(Cup eoh
cap ealus)
by sampling in plo s
o
75 hec a es o
oak
ha dwoods
(Que cus
obu ).
Howe e , he e o equi ed o
a sui able sample size ( hese au ho s conduc ed
35
d i e censuses), and also he
ime spen
in
o ganizing a su icien numbe o helpe s (obse e s, bea e s, and
hei hounds, e c.), should be conside ed when planning a d i e census. These
p oblems we e esol ed o SAez-Royuela and Telle ia (1988) who we e able o
p o i om hund eds o d i es o ganized
o
hun ing. Among he ad an ages o he
d i e census a e i s eliabili y and he possibili y o ob ain simul aneous da a on
o he animals, pa icula ly game species. I
is
impo an
o
no e ha he accu acy
o he esul s will be posi i ely co ela ed wi h he numbe
o
bea e s, and
nega i ely co ela ed wi h he size o a ea sampled (Telle ìa, 1986).
Undoub edly, he deg ee
o
dis u bance ha he d i e census in ol ed mus also
be conside ed; his
is
p obably no an ideal me hod o use in na u e ese es.
In
ou expe ience, we ha e ound
a
good app oxima ion be ween esul s
ob ained om d i e census ou o he limi s o Doiiana Na ional Pa k and hose
eco ded om o he densi y es ima o s p e iously de eloped
o
his a ea (see
below), a abou 1.7 oxes/km2.
205
SIGHTINGS
(NON
-
SYSTEMATIC OBSERVATIONS)
The basis o his me hod is o ge a egis a ion o any ox sigh ing in a gi en
a ea. Fo he analysis o such da a, sigh ings mus be e e ed o uni e o such
as he numbe o obse e s, ime spen in he ield, dis ance a elled, e c (Rau,
1988).
This
is
p obably he simples
o
all he a ailable me hods o es ima e ela i e
abundance o ed oxes, being especially ecommended o p o ec ed a eas, o
places whe e ield wo k is in p og ess ( esea ch, igilance, e c.). I implies many
man/hou s spen in he ield. Alien and Sa gean (1975), and Ha is and Rayne
(1986a)
employed sigh ings o oxes o calcula e abundance indices. Ne e heless,
he e y simplici y o his me hodology needs co ec ions
in
o de o alida e he
esul s and o ob ain ealis ic in e p e a ions o he da a. See o example Voig 's
(1987) commen s on he di icul ies in ol ed in de ining he co espondence
be ween a sigh ing index and
an
es ima e o ela i e abundance.
We ha e been able o de e mine
a
sui able adjus men o ou s udy a ea. Red
ox sigh ings due o keepe s, esea che s, and isi o s we e co ec ed agains
obse e numbe s. Iden i ica ion
o
animals wi h isual ags pe mi ed
us
o
calcula e he pe cen age o e-sigh ing
o
any indi idual. Finally, simul aneous
adio- acking da a we e used o es ima e p obabili y o a ox
-
c ossing di oad o
i eb eak inside i s home ange, whe e i was mos easily de ec able in he ield.
Compu ing hese ac o s,
Rau
(1988) ob ained a ox abundance index wi h ends
well acco ded wi h he ox densi y in Doiiana Biological Rese e as es ima ed by
o he mo e sophis ica ed me hods.
The me hod's economy, simplici y, easy s anda diza ion, and good adjus men
possibili ies wi h o he mo e eliable me hods, which a e also mo e expensi e (in
money and ime), a e good enough easons o using a da a base o ox sigh ings
as a measu e o popula ion ends.
This
app oach o densi y es ima o s has been
named
"
double sampling
"
(Ebe ha d and Simmons, 1987). Fox-sigh ings is only
one o he possibili ies (see below ack coun s), and can be applied
o
o he
species besides oxes.
DEN
COUNTS
Coun s
o
b eeding ox dens in la e sp ing o summe depending
on
he s udy
-
a ea (Lloyd, 1980), can be used o de e mine he absolu e abundance o he
species.
The
li e a u e
on
his subjec is ce ainly no lacking. The classic wo k o
Sa gean e al. (1975), p o i ing om he excellen isibili y o e hei s udy a ea
o coun s
o
ox dens om an ai plane, can be compa ed wi h coun s
accomplished on oo which equi es mo e s a , ield knowledge, e c. (S o m e
al.,
1976; Linds om, 1980; Hewson, 1986; P igioni e al., 1991).
P obably he majo ad an age o censusing oxes by coun ing hei b eeding
dens is he good le el o accu acy ob ained by his me hod. Sa gean e al. (1975)
de ec ed 84%
o
270
ox amilies
in
hei s udy a ea. Ob iously, some in o ma ion
206
has o be assumed such
as
he numbe o indi iduals pe den, e i o y size o a
ox
amily, e c. I he su ey is ca ied ou
on
oo , addi ional da a can be
egis e ed such as ood habi s o cubs e sus adul s (Delibes and Maiiez, 1984),
and compe i ion wi h o he species o den si es (Pigozzi, 1986). Den loca ion also
p o ides a good basis o u he wo k such
as
cap u ing (Zoellick and Smi h,
1986) and popula ion managemen (Zimen, 1980; Hewson, 1986).
TRACK COUNTS
IN
PERMANENT
TRANSECI'S
Di oads, i eb eaks, and o he simila clea ings a e commonly used by oxes,
o a elling, ma king, o es ablishing hei home ange bo de (Sa gean , 1972;
Fab igoulé and Mau el, 1982; Mau el, 1983, among o he s). This pa e n
o
space
use
is
no a cha ac e is ic unique o ed oxes. Pulliainen (1981) moni o ed annual
luc ua ions
in
ela i e abundance o ou species o ca ni o es, he ed ox
included, by skiing along
a
pe manen ansec o
6
kilome e s weekly du ing he
snowy season (No embe o Ap il). His esul s we e enhanced by simul aneous
obse a ions
on
oden ac i i y and habi a p e e ences
o
he ca ni o es du ing a
s udy pe iod long enough
-
13 consecu i e win e s
-
o desc ibe p eda o -p ey and
communi y dynamics. This me hodology has been used by Rau e
al.
(1985b) in
Sou hwes e n Spain (Do iana Biological Rese e)
o
es ima e ox densi y by ack
coun s
on
sand ansec s.
A
basic assump ion o his me hod is ha a linea ela ion exis s be ween he
numbe o acks (o o he signs) de ec ed and he ela i e abundance o he
species. Howe e , om ou expe ience, his is no always he case. F om
simul aneous adio- acking o oxes and su eying o a
1.2
km long sand ansec ,
a con e sion ac o was ob ained
o
ack/km o oxes/km (Se in e al.,
1987).
Each ox c ossed he ansec
3
imes
on
a e age in each 24 hou cycle. Howe e ,
he loca ion o he ansec g ea ly in luenced he esul s.
S ephenson (1986), and Schwa z and Becke (1988) ha e been in ol ed o
se e al yea s in de eloping simple echniques o es ima e popula ion ends in
Lynx
canadensis.
Thei design
is
a double sampling p ocedu e: simul aneous
moni o ing
o
lynx acks in snow ansec s and adio- acking
o
indi iduals du ing
24
-
48 hou s. Mo emen s
o
ma ked lynxes cons i u ing a andom subse o he
popula ion we e analysed by a ious me hods, including simula ion (Becke
in
p ess, in Schwa z and Becke , 1988).
SCAT COUNTS
IN
PERMANENT
TRANSECTS
The use o sca coun s o de e mine ox abundance has some simila i y wi h he
p e ious me hod:
a)
sampling is ca ied ou along delimi ed ansec s,
i
possible
pe manen in loca ion;
b)
a
s a i ied sampling design
is
also
p e e ed in o de o
a oid he e ec s
on
popula ion ends
o
seasonal changes in habi a use by oxes.
The sca coun p ocedu e, howe e , equi es special co ec ion ac o s (see below).
P obably no o he me hod has such long adi ion in he es ima ion o species
abundance (Kolb
and
Hewson, 1980; Pu man, 1984). Rau
e
al.
(1985a
and
b)
207
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