Social O ganiza ion and Fo aging in Emballonu id Ba s: III. Ma ing Sys ems
Au ho (s): J. W. B adbu y and S. L. Veh encamp
Sou ce:
Beha io al Ecology and Sociobiology
, 1977, Vol. 2, No. 1 (1977), pp. 1-17
Published by: Sp inge
S able URL: h ps://www.js o .o g/s able/4599115
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Beha io al
Ecology and Sociobiology
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Beha . Ecol. Sociobiol. 2, 1-17 (1977) Beha io al Ecology
and Sociobiology
? by Sp inge -Ve lag 1977
Social O ganiza ion and Fo aging
in Emballonu id Ba s
III. Ma ing Sys ems
J.W. B adbu y and S.L. Veh encamp
Depa men o Biology, C-016, Uni e si y o Cali o nia a San Diego,
La Jolla, Cali o nia 92093, USA
Recei ed June 12, 1976
Summa y. 1. A gene al model o ma ing sys em e olu ion in mammals is
de eloped, which akes in o accoun he di e en male s a egies o esou ce
de ense, emale g oup de ense, and male ma ing agg ega ions. The c i ical
en i onmen al a iables de e mining di e en ial de ensibili y o emales and
esou ces a e iden i ied by gene alizing he esou ce de ense model o O ians
(1969). The model is hen applied o a ailable da a on A ican an elopes
(Ja man, 1974) o es ablish a se o hypo he ical ela ions be ween ce ain
pa e ns o habi a use and ma ing s uc u es. The esul ing ela ions a e
only likely o apply o species in which ood de e mines emale dispe sion
and in which any esou ce de ense exhibi ed by males is di ec ed owa ds
ood supplies.
2. The ela ions de eloped o an elopes a e hen compa ed o ecen ly
published da a on ma ing sys ems in i e neo opical emballonu id ba s
(B adbu y and Veh encamp, 1976 a).
3. An elopes and he ba s a e ound o sha e he ollowing ea u es.
Species li ing in we and s able o es s end o be ine-g ained socially and
o ha e g oups consis ing o monogamous pai s o nes ed male- emale e i-
o ies. Species in mo e seasonal habi a s show an in e se ela ion be ween
he size s abili y o g oups and he du a ion o use o a gi en o aging
si e. As he model p edic s, in bo h g oups esou ce de ense occu s whe e
g oups a e leas s able and emale de ense whe e g oups a e mos s able.
Also as he model p edic s, he numbe s o emales accessible o each male
and he numbe o ep oduc i e males pe g oup can be an icipa ed in
each o he wo axa whe e e su icien da a o he c i ical a iables a e
a ailable.
4. An elopes and ba s di e in he ollowing ways. Whe eas body size
is a good p edic o o an elope habi a use and social dispe sions, i is
a poo p edic o o emballonu id pa e ns. Simila ly, al hough he numbe s
o emales pe male gene ally inc ease wi h g oup size in an elopes, his
co ela ion does no hold o he ba s in his s udy. These di e ences lead
o he conclusion ha applica ion o he gene al model canno be simpli ied
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2 J.W. B adbu y and S.L. Veh encamp
by measu emen o a ew a iables such as body size o g oup size, bu
ins ead will gene ally equi e ac ual measu emen s o he c i ical esou ce
dispe sion pa ame e s in he ield.
In oduc ion
The o m o mos animal social sys ems can be cha ac e ized by speci ying
he social dispe sion (i.e., g oup size and spacing), he ma ing sys em, and
he pa e ns o ju enile dispe sal and/o e en ion. Se e al au ho s ha e ecen ly
sugges ed ha selec ion ope a es ini ially on social dispe sion and ha subse-
quen e olu ion o ma ing sys ems can only occu wi hin he op ions allowed
by ha social dispe sion (Ja man, 1974; Alexande , 1974). A simila no ion
implici ly unde lies hose models o ma ing sys em e olu ion which ely on
esou ce dis ibu ions as en i onmen al de e minan s (e.g., O ians, 1969). In
a p io pape , we analyzed ield da a on se e al species o neo opical emballonu-
id ba s and a gued ha social dispe sion in hese species was p ima ily de e -
mined by a passi e mapping o he animals on o hei ood dispe sion (B adbu y
and Veh encamp, 1976b). In his pape , we wish o u ilize he same da a,
(B adbu y and Veh encamp, 1976a), o see (1) o wha deg ee p io de e mina-
ion o social dispe sion limi s ma ing op ions in hese species, and (2) whe he
cu en models o ma ing sys em e olu ion a e su icien o explain he obse ed
di e si y o emballonu id ma ing s uc u es. Me hods o da a collec ion can
be ound in B adbu y and Veh encamp (1976a).
Fo m and P ocess in Ma ing Sys em E olu ion
I will be impo an o ou analysis o emballonu id ma ing pa e ns o ou line
b ie ly he ypes o ma ing sys ems one migh expec o ind in mammals,
and he ways in which en i onmen al con ex s ha e been in oked as de e minan s
o one ype o he o he . A "classical" axonomy o mammalian ma ing sys ems
would dis inguish be ween monogamous pai s, ha ems, g oups o emales ended
by se e al adul males (he ea e called "mul i-male g oups"), and leks. We
eel ha a mo e use ul sys em can be based upon he s a egies a ailable o
males. We dis inguish h ee b oad ca ego ies:
1. Resou ce De ense. Males es ablish e i o ies con aining some esou ce ( ood,
wa e , nes ing o oos ing si es, e c.), equi ed by emales. Exclusion o o he
males and admission o emales only on condi ion o biased ma ing access
a e wo ways ha such e i o ial males migh gain in i ness. Examples include
many o he sa annah an elopes o A ica (Ja man, 1974).
2. Female De ense. I i is ad an ageous o o m s able g oups as an an i-p eda o
de ice, o inc ease o aging e iciency, o o sha e in pa en al du ies, males
may be able o exclude o domina e o he males and he eby enhance hei
own ma ing success. Mammalian examples include some baboons and ungula es
such as he eland and A ican bu alo (Kumme , 1968; Ja man, 1974).
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Ma ing Sys ems in Emballonu id Ba s 3
3. Male Ma ing Agg ega ions. Males may agg ega e a adi ional o species-
speci ic si es and be isi ed by emales only o ma ing. I emales a e able
o app oach he agg ega ion and make a choice o ma e, we may call he
agg ega ion a "lek". An example would be he Uganda kob (Buechne and
Schloe h, 1965). I an app oaching emale is mobbed by males and no ma ing
choice is possible, we may call he agg ega ion a "ma ing swa m" a e he
co esponding beha io in lying insec s (Downes, 1969). The la e beha io
appea s o occu in some empe a u e ba s p io o hibe na ion (Fen on, 1969).
The impo an di e ence be ween his sys em and a mo e classical lis ing
is ha i edi ec s he ocus away om he o m o he ma ing sys em owa ds
he condi ions which ha e gi en ise o hese o ms. This shi is in en ional
because i helps o cla i y he ac ha he same ma ing s uc u e may a ise
by se e al di e en ou es. Fo example, ha ems may a ise ei he by male
de ense o a esou ce o which g oups o emales come (e.g., an elopes), o
by he appending o an adul male o an exis ing emale g oup and de ense
o he g oup om o he males (e.g., Bu chell's zeb as). I is also he case
ha wi hin any one s a egy, say de ense o emale g oups, di e en ma ing
o ms may a ise, e.g., ha ems s. mul i-male g oups, depending upon ac o s
such as he size and he de ensibili y o he emale g oups.
A concep which is cen al o all heo ies o ma ing sys em e olu ion is
"de ensibili y" [o "de endabili y" as o iginally coined by B own (1964)]. De-
ensibili y e e s o he a io be ween he bene i s o con olling a e i o y
o g oup o emales, (as measu ed by an inc ease in su i al o ep oduc i e
success h ough enhanced access o esou ces o ma es), and he cos s o doing
so, (as measu ed by ime and ene gy spen in de ense, and isks incu ed as
a esul ). We expec de ense o be adap i e when he bene i s exceed he cos s.
I is now gene ally accep ed ha o a ixed cos , he amoun o esou ce
o numbe o ma es de ended mus be g ea e han some minimum alue be o e
bene i s exceed cos s, bu also less han some maximum alue a which compe i-
ion is oo low o wa an de ense (Schoene , 1971; Ca pen e and MacMillen,
1976). In o he wo ds, de ense is mos likely when he local densi y o esou ce
o emales is in e media e in alue. As a co olla y, he esou ce de ended mus
be exploi able long enough, o he g oup o emales sui ably s able in composi-
ion, o he de ende o ob ain su icien bene i s. A de ensible esou ce is
hus one ha is a ailable o mo e han some minimum amoun o ime and
which occu s wi hin a limi ed ange o local densi ies; a de ensible g oup o
emales is one which is mode a ely s able in composi ion and wi hin some
limi ed ange o g oup sizes.
I is also gene ally accep ed ha o a ixed bene i , he cos s o de ense
inc ease wi h he a ea (o pe ime e ) o be pa olled and wi h he densi y o
po en ial in ade s (Holmes, 1970; Schoene , 1971; Gill and Wol , 1975). Bo h
de ended a ea and in ade densi ies a e posi i ely co ela ed wi h cos s o de-
ense. Fo a ixed ceiling on a ailable ime o ene gy o de ense, i he e o e
ollows ha as in ade densi y inc eases, he de ende mus educe he size
o he a ea de ended. While his is gene ally so, he e a e excep ions which
a e c i ical o ou discussion. In gene al, he e a e wo ypes o e i o ial
de ense which can be dis inguished in animals (F e well and Lucas, 1969; F e -
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4 J.W. B adbu y and S.L. Veh encamp
well, 1972). Conside he common case in which e i o ies a e being es ablished
in a habi a wi h locally a ying densi ies o some c ucial esou ce. Suppose
ha po en ial se le s a e ela i ely able o assess hese local di e ences. Ini ially,
all se le s will es ablish e i o ies in he op imal po ions o he habi a wi h
each new in ade o cing comp ession o he e i o ies o ea lie se le s. E en-
ually, u he comp ession o exis ing e i o ies in he bes si es esul s in
an in ade ob aining less o al esou ce han i he es ablishes a la ge e i o y
in a less ich si e. Se lemen hen begins o occu in he nex mos op imal
si e and so on. As long as se le s and in ade s a e equally able o seize and
hold e i o y, a " ee" dis ibu ion o e i o ies will esul , in which e i o y
size and local esou ce densi y a e in e sely ela ed and all e i o ies will con ain
he same o al amoun o esou ce. F ee e i o ial dis ibu ions a e appa en ly
no uncommon in bi ds (S enge , 1958; Cody and Cody, 1972a, b; Ga ge ,
1975). I , on he o he hand, se le s a e be e able o de end e i o ies han
in ade s can in ade hem, comp ession o e i o ies in he be e si es will
hal a a lowe se lemen densi y han in he ee case. In ade s will hen
be o ced in o he less ich si es ea lie , and he o al amoun o esou ce
in e i o ies on he good si es will exceed ha in e i o ies on he poo si es.
This unequal pa i ioning o esou ces is called a "despo ic" dis ibu ion.
A despo ic ins ead o a ee dis ibu ion will a ise whene e he cos s o
a de ende o epelling each in ade a e no cons an o e all e i o y sizes,
bu ins ead dec ease as e i o y size is comp essed. I can also a ise whene e ,
ins ead o holding he o al amoun o cos s alloca ed o de ense cons an
o e all e i o y sizes, an animal is willing o inc ease hese alloca ions as
an in e se unc ion o e i o y size. Despo ic e i o ial dis ibu ions ha e been
epo ed o a a ie y o bi d species (B own, 1969; K ebs, 1971; Klomp, 1972).
In some o he ci ed examples, he e is e idence ha se lemen a low in ade
densi ies is ee, while ha a highe densi ies is despo ic. Some popula ions
always expe ience high in ade densi ies, ypically show despo ic beha io om
he s a , and exhibi " loa e " sub-popula ions which a e o ally p e en ed
om b eeding by e i o ial holde s.
The impo ance o he concep o de ensibili y in ma ing sys em e olu ion
is easily demons a ed using he model o Ve ne (1964) as modi ied by O ians
(1969) o he en i onmen al de e mina ion o monogamy s. polygyny. In his
model, all males a e p esumed o adop a s a egy o de ending a esou ce
which a emale equi es. O ians hen shows g aphically ha whene e he pa i-
ioning o he esou ces by e i o ial males is su icien ly unequal, emales
may do be e o ma e polygamously wi h an al eady ma ed male on a good
e i o y han o ma e monogamously wi h an unma ed one on a poo e i o y.
The model is in e p e ed by supe posing a ixed g id o e i o ies on o an
unde lying esou ce dis ibu ion. Whe e he esou ce is une enly dis ibu ed
in space, male e i o ies will a y in con ained esou ce, and polygyny can
esul ; whe e he esou ce is mo e uni o mly dis ibu ed, all male e i o ies
a e simila and monogamy is he esul . Following he sugges ions o Ve ne
and Willson (1966), O ians hen no es ha ce ain habi a s, such as ma shes,
do show he expec ed co ela ion be ween high local a iabili y in esou ce
densi ies and he occu ence o polygyny.
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Ma ing Sys ems in Emballonu id Ba s 5
While his model has had conside able popula i y and success in some speci ic
applica ions (e.g., Holm, 1973), i s use as a p edic o o ma ing sys ems is
limi ed by he necessi y o jus i y an implici assump ion. The na u e o his
assump ion becomes clea when we no e ha he O ians model is eally only
a special case o he F e well and Lucas (1969) pa adigm o e i o ial se le-
men . Seen in his way, monogamy is he esul o male and emale se lemen
his o ies which a e simila ly ee o simila ly despo ic; polygyny is he esul
o he special case in which male se lemen is mo e despo ic han emale se le-
men . Mo e impo an ly, he p esence o polygyny in one habi a and monogamy
in ano he can only be p edic ed when we can also p edic ha male e i o ial
se lemen will be su icien ly mo e despo ic in he i s habi a . We a e hus
aced, in applying he O ians model, wi h iden i ying wha makes one esou ce
dispe sion mo e de ensible han ano he . The basic model ci cum en s his
issue by aking he male dis ibu ion as a gi en, and showing how a subsequen
" ee" se lemen pa e n by emales will esul in monogamy o polygamy
depending upon ha ini ial male pa e n.
The iden i ica ion by O ians o ma shes and o he locally a iable habi a s
as being pa icula ly polygyny-p one is in ac an a emp o add ess he issue
o si e-speci ic de ensibili y. As no ed abo e, he supe posi ion o a ixed e i o-
ial g id on o a esou ce dis ibu ion will esul in g ea e a iance in he amoun
o esou ce pe e i o y as he poin - o-poin a ia ion in local esou ce densi y
inc eases. I one assumes ha a simila ly sized g id is supe imposed upon wo
habi a s ha ing he same o al amoun o esou ce bu di e ing in local "pa chi-
ness", we could p edic , using he model, ha polygyny is mo e likely in he
mos pa chy si e. The p oblem is he assump ion o simila e i o ial g ids
in he wo con ex s. When is i jus i ied o assume ha wo species o wo
popula ions will ha e simila g id sizes? Why can in ade males in he mo e
pa chy si ua ion no o ce subdi ision o he iche pa ches un il all males
ha e equal amoun s o esou ce? The model hus only wo ks i one assumes
ha bo h popula ions expe ience e i o ial comp ession down o some minimal
alue a which e i o ial de ense becomes en i ely despo ic, and ha his minimal
alue is simila o he wo popula ions. The i s assump ion p obably has
conside able alidi y; he second is mo e likely when ela ed species wi h simila
mo phologies and habi s a e being compa ed han when e y di e gen species
a e compa ed. We migh e en conside he possibili y ha wo e y di e gen
species ha e e y di e en minimal e i o y sizes. Imposing he e i o ial g id
o each on he same esou ce dis ibu ion would lead o polygamy in ha
wi h he la ge g id size and monogamy in ha wi h he smalle one. Thus
ei he di e ences in g id size o di e ences in esou ce dis ibu ion could lead
o di e ences in ma ing sys em.
We wish o o malize hese commen s as ollows. Suppose ha o a gi en
species in a gi en habi a , he e is a minimal e i o y size which has a mean
alue A. (A will a y somewha in he popula ion as a unc ion o size, age,
and expe ience o males; we shall jus conside he a e age alue). Suppose
ha males adop a s a egy o esou ce de ense, and ha emales dis ibu e
hemsel es eely acco ding o local abundances o esou ce. Le he a e age
densi y o esou ce wi hin he e i o y o male i be Ri. I a male has posi ioned
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6 J.W. B adbu y and S.L. Veh encamp
his e i o y o e pa o all o a ich pa ch o esou ce, Ri is la ge; i he
se les o e a less ich pa ch o be ween pa ches, Ri will be small. I B is
he amoun o esou ce equi ed pe emale, hen he numbe o emales in
he e i o y o male i is (ARi/B-1) i he male u ilizes he esou ce, o (ARi/B)
i he does no . No e ha a high a iance in he numbe s o emales pe male
among he males wi h emales is no a necessa y consequence o he model.
A la ge and uni o m pa ch o esou ce migh be se led by a ew e i o ial
males all wi h e i o y sizes o A and all wi h he same amoun o de ended
esou ce. While hese males would ha e simila ha em sizes, pa i ioning is
s ill despo ic since o he males ha e been excluded om he pa ch.
I ollows ha o use he O ians model, one is obliged o conside whe he
comp ession in he species being conside ed has eached a limi ing alue, and
whe he he A and B alues a e simila o he species o no . Whe e A and
B a e known o di e among species, i s ill may be possible o p edic ma ing
sys ems om Ri alues i he di e ences in A and B only augmen he di e ences
in Ri. Whe e no hing is known abou A o B, o whe e he deg ee o comp ession
canno be e alua ed, he model will no be use ul. Because unma ed bu ma u e
males occu in all o he species we shall conside , i seems likely ha comp ession
o a c i ical and despo ic le el has occu ed. We shall he e o e p esume ha
each o he popula ions discussed below is ope a ing a i s own alue o A.
We shall no p esume wi hou e idence ha alues o A and B a e iden ical o
di e en species. In gene al, one is obliged o es ima e hese alues whe e e
possible. I a popula ion is known o be despo ic, (as e idenced by he exis ence
o a loa e popula ion), an es ima e o A o ha popula ion in ha con ex
is he a e age size o e i o ies obse ed. Whe e ood is he p ima y esou ce
being de ended, an index p opo ional o B is he body weigh o emales
o he 3/4 powe (McNab, 1963). Whe e hese es ima es a e a ailable, and
whe e Ri alues a e known, i should be possible o de e mine which o wo
species is mos likely o be polygynous o which is likely o ha e he la ge
ha em size e en hough he absolu e alues o ARi/B a e no known. We shall
be mos conce ned wi h he maximal alues o Ri gi en a ce ain A and B
since hese se he uppe limi s on he numbe s o ma es ha a male can
ha e.
The p eceding sec ion inden i ies a se o speci ic a iables which can be
measu ed and used o p edic whe he males will be monogamous o polygynous
gi en a esou ce-o ien ed s a egy. I would seem ob ious ha we need a simila
pa adigm o emale-de ense s a egies. Suppose again ha compe i ion esul s
in comp ession o he a ea de ensible by a male down o some c i ical alue,
A, a which u he comp ession is unlikely. (No e ha while a ea de ensible
is impo an in emale de ense, i is no he objec o i . The di e ence is
pa icula ly impo an when males domina e as opposed o exclude o he males
in he g oup.) I he densi y o emales wi hin a male's de ensible a ea is deno ed
by Di, hen he expec ed numbe o emales pe male will be ADi. By analogy
wi h he p e ious discussion, species ha ing simila alues o A will di e in
ma ing sys em depending upon he alues o Di. The la e will di e depending
upon he o e all dispe sion o emales in he habi a . While emale dispe sion
a ies con inuously, o con enience we ecognize wo gene al cases. In he
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Ma ing Sys ems in Emballonu id Ba s 7
i s , emales a e soli a ily dispe sed ei he o op imize o aging o o educe
p eda ion h ough c ypsis (T eisman, 1975a, b; Ja man, 1974). Female g oup
size, which we deno e by P, is 1. The e a e h ee sub-cases depending upon
whe he maximal alues o ADi a e less han, equal o, o g ea e han one.
ADi < 1 is unlikely since males canno b eed unde hese ci cums ances. ADi= 1
implies ha males and emales a e simila ly dis ibu ed and mos likely li e
in monogamous pai s. I will occu whene e A o Di o bo h a e small. AD,> 1
implies ha he de ended a eas o males con ain a numbe o soli a y emales.
This "nes ed" sys em appa en ly occu s in a numbe o oden s, p ima es,
and ungula es (B own, 1966; Dubos , 1970; Cha les-Dominique, 1972). When
P> 1, he second gene al case, hen emales li e in g oups which mo e as
uni s h oughou he sui able habi a . Again we ejec AD,< 1 as unlikely. When
AD= 1, hen we expec o ind g oups which ha e equal numbe s o males
and emales and mos likely consis o monogamous pai s. An example appea s
o be he la ge oden , Dolicho is pa agonum (Genes and Dubos , 1974). When
AD> 1, we may ge se e al ma ing s uc u es depending upon he ela ion
be ween AD, and P. I ADi=P, we expec o ind ei he one-male ha ems,
as occu in zeb as (Klingel, 1972) and Hamad yas baboons (Kumme , 1968),
o mul i-male oops wi h s ong male ep oduc i e dominance hie a chies as
in sa annah baboons (Hall and DeVo e, 1965). In mul i-male g oups whe e
one male does mos o he ma ing, he p esence o o he males appea s o
be due ei he o he e en ion o male o sp ing (Eisenbe g e al., 1972), o
he need o coope a i e mul i-male de ense when p eda o s a e common and
la ge in size (Denham, 1971). I ADi<P, hen we expec se e al adul males
o accompany he emales and all o pe o m some o he ma ing. This occu s
in a a ie y o la ge-sized A ican bo ids (Ja man, 1974). We no e ha AD,<P
ei he because he g oup o emales is so la ge ha i co e s an a ea la ge
han A, o because e en hough P is small, he emales occu a la ge indi idual
dis ances and hence Di is small.
We ha e now discussed he c i ical a iables which mus be measu ed o
an icipa e he ma ing o ms gi en ei he esou ce-o ien ed o emale-o ien ed
male s a egies. To comple e a p edic i e heo y o ma ing sys ems, we need
o add wo ela ed componen s. The i s is o iden i y hose habi a s and
hose habi a a iables which p edispose males o adop ei he esou ce de ense
o emale de ense o nei he . On he basis o ou p io conside a ions, we
p esume ha a habi a mus mee he ollowing h ee necessa y condi ions
be o e a male should p e e en ially adop esou ce de ense: (1) esou ces a e
ene ge ically de ensible; (2) hey a e locally a ailable o su icien ly long ha
a male can ex ac bene i s; and (3) emales and esou ces a e so dis ibu ed
ha ARi/B>ADi. Simila ly, a habi a will mos likely lead o emale de ense
i i mee s he ollowing h ee necessa y condi ions: (1) emale g oups o pa s
o g oups a e ene ge ically de ensible; (2) g oup size and/o composi ion a e
su icien ly s able o males o gain bene i s; and (3) AR/ B<ADi o all limi ing
esou ces. (When nei he esou ces no emales a e de ensible, o when nei he
is su icien ly s able in ime, we belie e males a e o ced o adop he "de aul "
s a egy o male ma ing agg ega ions. E idence o his iew will be p esen ed
in a subsequen publica ion). Co ela ions be ween habi a s which mee one
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8 J.W. B adbu y and S.L. Veh encamp
se o condi ions o ano he and male s a egies will indica e whe he he condi-
ions a e su icien as well as necessa y. The second ask is o combine es ima ed
alues o A, B, Ri, Di, and P o p edic he inal o m o he ma ing sys em:
monogamous pai s, pe manen ha ems, mul i-male g oups wi h all males ma ing,
mul i-male g oups wi h dominance, e c.
We canno in his pape de elop a gene al synopsis o ma ing sys ems and
habi a con ex s. Ins ead, we shall concen a e on he pa icula subse o species
in which ood cons i u es he bes de ensible esou ce o males and in which
emale dispe sion is de e mined p ima ily by ood dispe sion. In o he wo ds,
we shall ocus on species o which bo h Ri and Di a e di ec unc ions o
he ood supply. This es ic ion appea s o be sa is ied o mos o he A ican
bo ids ecen ly e iewed by Ja man (1974). These animals appea o show
male de ense o ei he emales o ood supplies, and a leas he uppe limi s.
on g oup size and g oup spacing can be p edic ed wi h con idence om knowl-
edge o hei ood habi s and ood dispe sions.
All an elopes end o a o ood sou ces which a e high in p o ein ela i e
o ibe con en . Whe e di e se plan o gans a e a ailable as ood, an elopes
will selec hose o gans wi h highes p o ein con en s; whe e di e se o gans
a e no a ailable, an elopes will seek ou hose plan s whose phenology is a
a s age (e.g., elea ing, lowe ing, e c.), leading o high p o ein con en s. These
pa e ns a e ied o habi a s as ollows. Species o an elopes which li e in
we and s able o es s encoun e high plan species di e si ies and low seasonal
synch ony in phenological ac i i y. They hus can specialize bo h on speci ic
o gans and on pa icula s ages o phenological ac i i y. Thei ood is essen ially
" ine-g ained" in dispe sion: ha is, i occu s in small pa ches o low ichness,
(measu ed in animals eedable), and bo h simul aneous and successi ely a ailable
pa ches occu a high densi ies (c . B adbu y and Veh encamp, 1976b o e mi-
nology). As Ja man (1974) has shown, such species end o be socially " ine-
g ained" as well: ha is, hey occu in small g oups and ha e small annual
home anges.
An elopes in mo e seasonal habi a s expe ience a a he di e en ood dispe -
sion. Typically, he ege a ion consis s o la ge pa ches o lowe plan species
di e si y and g ea e local phenological synch ony han occu s in o es . O en
he habi a consis s o a mosaic o such la ge pa ches: hill op and sumps in
olling ca ena, pa ches o ees sepa a ed by pa ches o g assland, e c. While
pa ch size is gene ally la ge han in o es , i a ies om small clumps o
bushes o eno mous homogeneous expanses o g asses. Nea ly all an elopes
in such habi a s show seasonal mo emen s be ween pa ches o ege a ion as
hey become seasonally ac i e phenologically. Howe e , he species di e in
he equency and in he ange o hese mo emen s. An elopes o in e media e
size appea o be mode a ely speci ic abou wha plan pa s a e ea en, bu
less speci ic abou he plan species and he deg ee o phenological ac i i y.
As a consequence o he la e wo biases, hey end o emain wi hin a gi en
pa ch o longe and a e mo e willing o mo e om one ege a ion ype in o
an adjacen bu e y di e en ype han a e la ge bo ids (Bell, 1970; Ja man,
1974). The abili y o use adjacen pa ches in he mosaic and o emain longe
on any gi en pa ch leads o lowe annual home anges han in la ge species.
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Ma ing Sys ems in Emballonu id Ba s 15
despi e conside able e o by se e al ield wo ke s (Lopez-Fo men , 1976; B ad-
bu y and Veh encamp, 1976a). I is ex emely di icul o ma k enough indi id-
uals in he la ge colonies o his species o de e mine whe he ei he emales
o esou ces a e egula ly de ended. I is clea om bo h s udies ha i males
a e de ending esou ces, hey a e doing so only occasionally and o sho
pe iods. Mos indi iduals in a gi en colony appea o use se e al o aging
si es each nigh and o change o aging loca ions equen ly du ing he yea .
G oup size, as well, appea s o be highly labile in his species. Some o his
luc ua ion is appa en ly due o di e en ial habi a use and di e en ial p open-
si ies o make seasonal mig a ions in he wo sexes (Lopez-Fo men , 1976).
The a ailable da a hus sugges ha bo h g oup s abili y and he du a ion
o use o o aging si es a e low in his species. These ac s, plus he obse a ions
o inc eases in he p opo ions o males and in male calling ac i i y in la ge
colonies du ing he sho annual copula ion pe iod, all sugges ha male ma ing
agg ega ions may be he mos likely ma ing sys em o hese ba s. Seasonal
ma ing "swa ms" a e known o occu in a a ie y o empe a e insec i o ous
ba s and seem o be associa ed wi h ma ing du ing pe iods o high popula ional
lux (as he ba s mig a e o hibe nacula), and dwindling le els o a ailable
ood. These condi ions a e analogous o wha we ha e ou lined abo e o
B. plica a. This p edic ion will become es able as we es ablish mo e comple ely
ma ked popula ions o hese ba s.
I is wo h summa izing he deg ee o which he an elope ends ha e o
ha e no been con i med in he emballonu id s udy. On he plus side, i does
seem o be he case in bo h g oups ha ine social dispe sions, and/o small
g oups, a e p ima ily ound in we and s able o es s and end o consis o
monogamous uni s. I also appea s ha in seasonal habi a s, s abili y o g oup
sizes and du a ion o pa ch use a e in e sely ela ed, and his leads o p edic able
biases owa ds adop ion o emale o esou ce de ense s a egies. Howe e ,
in B. plica a, his ela ion ails. Whe he his is due o he much coa se social
dispe sion o his species o o i s much mo e seasonal and a id habi a is
no known. Las ly, whe e da a a e a ailable, bo h he numbe s o emales
pe male and he numbe s o ep oduc i e males pe g oup a e di ec ly ela ed
o alues o A, Di, Ri/B and P. On he debi side, i is no ue, as i is
in an elopes, ha smalle -bodied species o ba s end o li e in he mo e s able
and di e si ied habi a s. I is also no ue ha social dispe sion becomes mo e
coa se as a unc ion o body size. The ailu e o his an elope co ela ion in
he ba s, e en hough he la e show a signi ican ela ion be ween local densi ies
o insec p ey and body size, is due o he ac ha pa ch size is o ally un ela ed
o body size. Thus pa ch ichness, which is he p oduc o local p ey densi ies
and pa ch size, and which de e mines g oup size, ends o ha e no ela ion
o body size. Simila ly, o aging anges, which mus be limi ed in pa by
he dis ance a ba can ly, a e mo e dependen upon wing shapes han hey
a e on body sizes a leas wi hin he s udied species (B adbu y and Veh encamp,
1976a). A inal end in an elopes is an inc ease in Di as P inc eases. Again,
because o he play-o in local p ey densi ies and pa ch size in de e mining
pa ch ichness and g oup size, he co ela ion be ween hese a iables o ba s
is close o ze o.
The di e ences no ed abo e be ween he wo g oups do no con adic
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16 J.W. B adbu y and S.L. Veh encamp
he basic p emise in bo h s udies: ha is, ha social dispe sion is p ima ily
de e mined by he ood supply and ha selec ion o ma ing s uc u es occu s
wi hin he bounds se by a gi en emale dispe sion. The e is no e idence in
ei he s udy ha ma ing sys ems d i e social dispe sions. Wha is b ough in o
ques ion by he di e ences be ween he wo g oups o mammals is he no ion
ha such simple a iables as body size and habi a ype will e e se e as
good p edic o s o ma ing sys ems e en wi hin axa ha ing a simila dependence
on a common esou ce. Ins ead, i appea s ha o each g oup o animals,
ield da a mus be p o ided o de e mine how he habi a is expe ienced by
he di e en species. Mo e speci ically, one mus know (1) he a e age size
o esou ce pa ches; (2) he ypical local densi ies o esou ce wi hin an ac i e
pa ch; (3) how a an animal mus a el be ween successi ely a ailable pa ches
and how long a gi en pa ch is used; (4) how consis en is he ichness o
successi ely a ailable pa ches and wha a e he cos s o an animal o changing
g oups when a ia ion is high; and (5) he size o A o each species and
whe he se lemen densi ies o ce comp ession o his alue. Whe e wo ela ed
species using he same o simila habi a s show some di e gence in esou ce
p e e ences, any o all o he alues o hese pa ame e s may di e and he
wo species can be expec ed o ha e di e en social dispe sions and ma ing
sys ems as a esul . In sho , he e seem o be no sho -cu s o di ec measu emen
o esou ce dispe sions i we wish o p edic ma ing sys ems in mammals. How-
e e , once hese a e known, social dispe sion ough o be p edic able and ma ing
sys ems de i ed as a esul .
Acknowledgmen s. The au ho s wish o hank D . Pe e Ma le , D . Donald G i in, D . Mike
Bake and ou o he colleagues a Rocke elle Uni e si y o eading ea lie d a s o his manusc ip
and o e ing many help ul commen s. This wo k was suppo ed by NSF G an GB-30478 o he
i s au ho .
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