AUTHORS: Patricia Black-Decima, Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán (UNT); Alejandra Hurtado; Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán (UNT); Mirta Santana, Facultad de Medicina, Universidad Nacional de Tucumán (UNT); José Mauricio Barbanti Duarte, Nucleo de Pesquisa e Conservacao de Cérvideos (NUPECCE), Faculdade de Ciencias Agrárisa e Veterinarias, Universidade Estadual Paulista (UNESP)
ABSTRACT: Deer vocalizations have been shown to be extremely varied and conspicuous in their frequency and temporal parameters, especially in rutting calls of Old World male polygynous deer. These calls also convey important information about the size and quality of the caller through their pitch and formant parameters which is used by other males and females in their evaluation and mate choice [1]. In contrast, little is known about vocalizations in New World Odocoileine deer. The males produce courtship grunts, they produce snorts instead of barks in alarm situations and females and fawns have calls that seem similar to those in Old World deer. Only a few spectrograms have been published on vocalizations in the white tailed deer, Odocoileus virginianus, in North America [2]. A few recordings of moose (Alces alces) and reindeer (Rangifer tarandus) have also been done. Male mating calls have also been used to make a phylogeny of 11 representatives of the family Cervidae [3]. However, in these studies, Neotropical deer are not included.
Neotropical deer comprise 6 genera and at least 17 species [4]. The most speciose genus is Mazama, the brocket deer, currently with 10 species accepted. M. americana, the largest species, probably includes several cryptic species. All brocket deer are very similar morphologically and it is difficult to distinguish between species of similar size. They are solitary, territorial and live in regions of dense cover.
The objective of this study was to record the vocalizations and analyze the pitch parameters of individuals of Neotropical species available, especially Mazama in order to characterize them and to see 1) whether there are reliable differences among species that could be used taxonomically 2) possible functions 3) whether there are individual differences that would permit individual identification.
Recordings were made at the Horco Molle Experimental Reserve in Tucuman, Argentina, and at the Deer Research and Conservation Center, FCAV, UNESP, Jaboticabal, SP, Brazil. Deer recorded included the red brocket Mazama americana (5 males, 4 females), the brown or grey brocket M. gouazoubira (4 males, 3 females, 1 fawn), the Amazonian brown brocket M. nemorivaga (3 males), the Brazilian dwarf brocket M. nana (1 male), the white tailed deer Odocoileus virginianus (1 male), taruka Hippocamellus antisensis (1 male) and swamp deer Blastocerus dichotomus (1 male). Captive deer were allowed to interact with humans (in the case of hand-raised deer) or with a female deer. Adult male deer vocalized as they showed sexual behavior (courtship licking, mounting attempts). Some females vocalized with a male or when they heard humans. Recordings were made with a digital recorder and shotgun microphone and analyzed with the programs Audacity and Praat 5.1.37 DSP. The Sound Edit menu was used to determine fundamental frequency F0 (pitch) and duration parameters. Pitch parameters analyzed included F0 Mean, Maximum, Minimum, and the frequency at the beginning, middle and end in each call. Vocalizations of 3 species of Mazama, in which various individuals were recorded, were analyzed statistically with a linear hierarchical model, using species, sex and age as fixed variables and individual, call and recording year as random variables.
All vocalizations were short duration, low intensity bleats, usually produced repeatedly with an interval of one to 30 sec or more. Some individuals produced bouts with from 3 to 18 bleats with intervals of < 1 sec. Durations of bleats ranged from 0.05 to 0.3 sec, with some exceptions (one female). Frequencies ranged from 100Hz for O. virginianus to 300-400Hz in other species and up to 600Hz in the fawn. There was great variation in parameters between calls and individuals. Frequency parameters were not related to body size. The statistical analysis of 3 brocket deer species showed considerable overlap among species and significant individual variation in all cases (p<0.001). There were no differences between sexes. Among the males, M. nemorivaga had durations significantly longer (p=0.012) than the other two species, while all the frequency parameters were significantly higher (p=0.011-0.017) in M. americana than in the other two species. There are significant differences with age in M. gouazoubira.
There are differences in species in the acoustic parameters of their bleats, but these differences are not great enough to distinguish reliably among species. Individual differences are striking, but the significance of this is not clear in solitary species where mate choice is limited and reproductive barriers not well developed [5, 6]. Also, under the conditions of these recordings, only a minority of the individuals vocalize. Males seem to vocalize when they are sexually aroused and courting a female and the female could possibly be stimulated by the males’ calls. Some females of M. americana vocalized when they were with males, but it seemed to be in rejection of the males’ advances. Females of M. gouazoubira and M. nemorivaga were not observed to vocalize in the presence of males. Most female brown brocket vocalizations were observed in juveniles and may be a retention of infantile behavior, since all fawns vocalize. No mothers with fawns were available for recording in these experiments, so the characteristics of these calls are not known.
This study confirms again that, between species, F0 is not related to body size. Two of the larger species (M. americana, H. antisensis) had the highest frequencies, while there was considerable overlap among the other species of Mazama, despite considerable size differences between M. nana and the other two.
