Behaviour 143, No 6 (June 2006)
http://www.ingentaconnect.com/content/brill/beh/2006/00000143/00000006
(Abstracts below)
Darden, SK & T Dabelsteen (2006) Ontogeny of swift fox Vulpes velox
vocalizations: production, usage and response. Behaviour 143: 659-681.
Lamml, M & B Kramer (2006) Differentiation of courtship songs in parapatric
sibling species of dwarf stonebashers from southern Africa
(Mormyridae, Teleostei). Behaviour 143: 783-810.
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Darden, SK & T Dabelsteen (2006) Ontogeny of swift fox Vulpes velox
vocalizations: production, usage and response. Behaviour 143: 659-681.
Three processes, production, usage, and response, can be used to describe vocal
ontogeny. They may develop independently of each other for a given vocalization
and a given species as a result of the different selective pressures associated
with each process. We have investigated vocal ontogeny in the swift fox Vulpes
velox, using recordings and observations of captive foxes from the time of
natal den emergence (age 3-4 weeks) to the time of natal dispersal in the wild
(age 4-5 months). We first classified adult vocalizations used during the
mating and pup rearing seasons into vocal types (19 types in total) and found
that swift foxes have a vocal repertoire comparable in size and diversity to
other canids. The repertoire of juvenile foxes contained 16 of the 19
adult-type vocalizations and one juvenile vocalization by age 10 weeks, after
which no new types appeared by the end of the study period. Two of the 3 adult
vocalizations not observed in juveniles appear to be associa
ted with mating and possibly territoriality and the third is a high intensity
alarm vocalization. Apart from 3 vocal types (1 alarm and 2 non-agonistic),
once vocalizations had appeared in the juvenile repertoire, they did not seem
to change in context over time. Juvenile responses to 5 vocalizations emitted
by adults (3 alarm, 1 agonistic, and 1 non-agonistic) appeared to change with
increasing age to approach adult-type responses. The emergence of these
adult-type responses to 2 of the 3 alarm vocalizations coincided with their
first appearance in the juvenile repertoire. The results indicate that there is
variation in the degree (in terms of the number of vocal types) of modification
over time among the three processes.
Lamml, M & B Kramer (2006) Differentiation of courtship songs in parapatric
sibling species of dwarf stonebashers from southern Africa
(Mormyridae, Teleostei). Behaviour 143: 783-810.
We describe the nocturnal courtship songs of male dwarf stonebashers,
Pollimyrus castelnaui, from the Okavango River and its inland delta. We
examined the question of whether the songs are sufficiently differentiated from
those of its parapatric sibling species, the only recently discovered P.
marianne from the Upper Zambezi River, to form a potential cue for mate choice.
Both species vocalised two sound types in courtship, the moan and the grunt,
which they combined into long songs in similar fashion. However, one sound type
was clearly differentiated: while P. castelnaui moans were of a husky quality
and composed of three or four broadband formants, P. marianne moans were more
tonal, with a single spectral line dominating the first and any higher formants
(and a smaller bandwidth BW?10 dB for the dominant frequency of the first
formant). Moan and Grunt Duration and the moan Pulse Group Period (mPGP) were
longer, and the latter more variable, in P. castelnaui compared to P.
marianne (range of mPGP: 10-30 ms in P. castelnaui, 7-16.7 ms in P. marianne).
P. castelnaui grunts were of longer duration and composed of more pulses than
those of P. marianne. A single male from the contact zone between the Okavango
and the Zambezi, the lower Kwando River, resembled P. castelnaui in moan BW?10
dB but P. marianne in Moan Duration and mPGP. Both southern African species
thus vocalise in a species-specific fashion. Since in both species several
characteristics of both moans and grunts show high between- and low within-male
variability, mate choice may be selective for individual high-quality males
characterised by acoustic features.
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