SCIENT. PAP. NAMIB DESERT RES. STN, NC). 46 83 THE CALL OF THE BARKING GECKOS (GEKKONIDAE : REPTILIA) by W. D. HAACKE Transvaal Museum. Pretoria (With 4 figures and 1 colour plate) interpretations. Brain (1962), when revising the genus and describing P. carpi, repeated most of fie Gekkonjdae are the only lizards with true them, adding his own observations and mentioning cal abilities and of this group the southern a call heard by Dr, Koch at Gobabeb, which had rican genus Ptenopux js probably one of the more clicks and followed in quicker succession than )st vociferous. The call mnsists of a series of is known for gnr~ulm.It was then assumed to haw quick ) clicks, ticks or chirps, which are uttered in been the call of carpi, but was later found by the 1 succession. 1 Calls are usually uttered in reply to author to be thaJ of koc?~i,a species still undescribed 0 others, for which reason the type species was called in 2 1962. When describing kochi in 1964 the author d Ptenopus garrulus. When describing this species in first mentioned a different call for each of the e t 1849, Sir Andrew Smith wrote: thrce species. At that stage it had aIready been a d noticed that not only a remarkable interspecific ( Tn the localities in which it occurs, many jndividuaIs r may be seen peeping from their hiding places, each but also intraspecific variation in the calls existed e h uttering a sha~sound, somewhat like chick, chick; and that fluctuations in humidity and ternpr?rature s i and the number thus occupied is at times so great and l affected the reaction of She geckos. Since then an b the noise so disagreeable, as to cause the traveller to u change h is quarters." attempt has been made to obtain more detaiIed P e information about the call of Ptenop~cs,especially h t At present three species are known, of which two P. gwrulus. The above-mentioned onomatopoeic re- y were described within the last seven years. Each productions might, ta some extent. reproduce the b d species has a characteristic call. Ptmopus is a sound and give some impression of the call, but, e t terrestrial genus and each specimen lives in a self- unless actual recordings are available, do not suppIy n a made burrow. The call is uttered by the male only any information regarding the duration, rhythm, r g and the functional significance is still uncertain pjtch and other characteristics which are even more e c but probably is associated with territoriality and difficult to describe. Because of these shortcomings n e e attraction of females. Vocal activity usually an attempt was made to produce better comparative c i l arts towards sunset. reaching its peak just after means tape recordings subsequent material by of and r nset e before darkness falls. Silence usually foll- analyses. d vds, but loud choruses may continue right through n clicks u Each call consists of a series of uttered in the night and isolated calls may be heard during y quick succession. Although Broughton (1963: 16) a the day. No calls are heard during the winter w and even in there may be silence defines '"the shortest unitary rhythm element of e months summer t fo. sound emission that can readily be distinguished as a r weeks. The ~rrelationbetween season, weather such by the unaided human ear" as a 'chirp', the G an ~dvocal activity is still not clear. t author wrefers the term 'click' for the individual e n sound is i Since the original description by Smith a number pulses of which a caII consists, as it a b have and better description of these staccato sounds. A con- a authors described the call Loveridge S 947: 35) summarized the various onomatopoeic siderabIe variation in the number of cLicks per call y b d e c u d o r p e R 84 DR. FITZSEMONS COMMEMORATIVE VOLUME and the rate at which the clicks were uttered has of the Research Station at Gobabeb, while other been observed. observations were made during various trips to the northern Transvaal, Botswana, the northcrn Capc There has been some speculation in the past con- Province and South West Africa. In a number of cerning the sound-producing mechanism involved, places the frequency distribution of the number of and Loveridge (1947: 14 quoted by Brain 19621 clicks per call was established by writjng dawn the assumed that the sound was produced by "the number of cIicks for a long series of calls at a given sudden removal of the fleshy tongue from contact locality. This was done for P. garrulus only, as in with the palate'bwhile Goin and Goin (1962 : 267) the call of kochi the repetition rate of the clicks thought "that the sound is perhaps produced by is so high that it: is impossible to make accurate clicking the broad tongue agajnst the roof of the counts, while on the few occasions that the call mouth." As the larynx of gekkonids has membran- which is assumed to be that of carpi was heard, eous folds which can be considered to be vocal chords no recording material was avaiIable. (Keleman 1963 : 491 and Tembrock 1959: 37), this family is the only one amongst the lizards with true The recordings were a11 made on a NAGRA ID vocal abilities. The presence and structure of this portable tape-recorder and a Beyer M88 microphone organ has not yet been investigated in Ptenopm, was used. The recordings in the central Namib but, as this genus is so exceptionalIy vocal, it is Desert were made by placing the microphone on provisionally accepted that the larynx is well the ground about 12 inches away from the hole of developed and that the sounds are produced by It. the gecko, while in the Gernsbok Park the micm- phone was used in connection with a 36 inch para- The function of the call is still uncertain. Mertens bolic reflector. The recordings were analysed on a (1946: 36) suggests that it is part of territorial Kay Electronic "Sona-Graph" 6061A while us in^ behaviour, but may also serve to attract females. a narrow band selector. A frequency spectrum of a This is possible, as no two holes were observed to signal Is thus obtained. Signals or parts of signals be closer together than about two feet, which may tasting not more than 2.4 seconds and a frequency indicate that females also show some degree of range betwecn 85 cycles and 8 kilocycles arc territoriality, which is unusual. However, as only r~cordedon a strip of spe-ial paper. This recording malcs have been observed calling, it is uncertain in is known as a "sonagram" (Andrieu 1963: 42) and what way females would define their territory. It by using the scale marked on The recording drum ) has been observed that the female of the Tokeh 1 of the "Sona-Graph'" the various time factors 1 (Gekko gecko) is attracted by the call of the male 0 involved can be measured. The total time for various 2 (Mertens op. dt.). During the middle of October calls and their "puhe repetition rate" (Broughton d e 1965 on the farm De Waal, Gobabis district, South The t 1963: 6) was thus established. first measur- a West Africa, just after dark, six specimens of ement was obtained by measuring the distance d ( were in P, garrulus colIected while running the between the beginning of the first and the end of r e road in the lights of an oncoming truck. At the the last cIick, while the second was estabIished by h s time other geckos were still calling. As all the i measuring the time-lapse between the beginning of l b spmimens collected were females, it is possjbIe that each pair of consecutive clicks in a call. For lack u this was a case where the females were responding P accurate of a more term one of the latter measur- e to the call of the males. h ements is hereafter referred to as an "interval". No. t attempt was made at this stage to evaluate the y Hunsaker et al. (1968) found indications that b certain geckos, for example Hemidactylecs, may not frequencies of each click. d e be able to hear their own calls, as their auditory t According to the Davis (1948) system the loci n thresholds are not in a direct reIationship to their a of the localities where these observations were made r vocaI ability. Although electro-physiological expe- g are as follows: Annisfontein 1628 Ed, Daberas 1628 e riments have not yet been carried out with Pteno- c DC,De Waal 1823 Bd, Gobabeb 1523 Ca,Gorob Mine n pus, to check their hearing, behavioural observations e 1523 Cb, Hotsas 1522 Ca, Nossob Camp 2025 BC, c i certainly showed clear reactions to the calls of other l Sendelingsdrif 1628 Bb, Swartpoort 1628 Eb. r individuals. e d n u DISCUSSION AND RESULTS y METHODS AND MATERIAL a w Ptenopus garmlus (Smith) e As Ptenopug rarely calls in captivity, all the t a recordings and behavioural observations had to be Under normal conditions garrulus calk in the G made in the field. Distress and agressive calls as late afternoon towards sunset, with greatest activity t e defined by Hunsaker et al. (1968) are ignored in just after sunset, quietening down rather abruptly n i b this paper. Tape-recordings were only made at the as soon as darkness falls, However, especially during a Camp S Nossob in the Kalahari Gemsbok National rainy weather, loud concerts may continue through y Park and in the central Namib Desert in the vicinity the night, only stopping after sunrise.