Editorial
THE MANAGING EDITOR'S REPORT ON THE JOURNAL OF ZOOLOGY FOR 2000
- Juliet Clutton-Brock
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- 17 May 2001, pp. i-iv
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The Editors decided, during the year, that there was really little need for a Short Communications Section and it would be more effective to incorporate short papers into the body of the Journal. Great thanks therefore go to Martyn Gorman for his many years as Editor of the Communications from the Mammal Society and latterly for his editing of the Short Communications.
By the end of 2000, the majority of the members of the Editorial Board had completed a five year term and an editorial decision was taken to replace the Board with a small team of international Editorial Consultants who would be asked to act as ambassadors for the Journal as well as giving advice on editorial matters. I should therefore like to thank all the retiring members of the Editorial Board for their work on the Journal and welcome the new Editorial Consultants whose names are given on the inside front cover of this issue.
During 2000, 160 papers were published in the twelve monthly parts of volumes 250–252 and there was approximately eleven months between acceptance of a paper and its publication. Our aim is to reduce this time to a maximum of ten months from now on.
Over the year, 286 manuscripts were submitted to the Journal and reports were written on them by 471 referees, whose names are listed below. As in previous years, I should like to make full acknowledgement of the generosity of these referees in both their time and expertise, without which the Journal could not survive. I should also like to thank all the authors who have sent in colour slides for possible reproduction on the covers.
Research Article
Censusing and monitoring black rhino (Diceros bicornis) using an objective spoor (footprint) identification technique
- Zoë C. Jewell, Sky K. Alibhai, Peter R. Law
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- 17 May 2001, pp. 1-16
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An objective, non-invasive technique was developed for identifying individual black rhino from their footprints (spoor). Digital images were taken of left hind spoor from tracks (spoor pathways) of 15 known black rhino in Hwange National Park, Zimbabwe. Thirteen landmark points were manually placed on the spoor image and from them, using customized software, a total of 77 measurements (lengths and angles) were generated. These were subjected to discriminant and canonical analyses. Discriminant analysis of spoor measurements from all 15 known animals, employing the 30 measurements with the highest F-ratio values, gave very close agreement between assigned and predicted classification of spoor. For individual spoor, the accuracy of being assigned to the correct group varied from 87% to 95%. For individual tracks, the accuracy level was 88%. Canonical analyses were based on the centroid plot method, which does not require pre-assigned grouping of spoor or tracks. The first two canonical variables were used to generate a centroid plot with 95% confidence ellipses in the test space. The presence or absence of overlap between the ellipses of track pairs allowed the classification of the tracks. Using a new ‘reference centroid value’ technique, the level of accuracy was high (94%) when individual tracks were compared against whole sets (total number of spoor for each rhino) but low (35%) when tracks were compared against each other. Since tracks with fewer spoor were more likely to be misclassified, track sizes were then artificially increased by summing smaller tracks for the same rhino. The modified tracks in a pairwise comparison gave an accuracy of 93%. The advantages, limitations and practical applications of the spoor identification technique are discussed in relation to censusing and monitoring black rhino populations.
Proboscis morphology and food preferences in nymphalid butterflies (Lepidoptera: Nymphalidae)
- H. W. Krenn, K. P. Zulka, T. Gatschnegg
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- 17 May 2001, pp. 17-26
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Many species of nymphalid butterflies only exceptionally visit flowers and feed instead on tree sap, juice of rotting fruits and other decaying substances. To investigate whether the proboscis morphology of these non-flower-visiting Nymphalidae differs from that of nectarivorous butterflies, representatives from 64 nymphalid species with known feeding preferences were examined. Morphometric comparison of the proboscis revealed characteristic differences in proboscis length, tip-region length, wall composition, and number and shape of proboscis sensilla between these two feeding guilds. The investigated non-flower-visiting species belonging to Apaturinae, Limenitidinae, Morphinae, Brassolinae, Nymphalinae and Satyrinae, possess a relatively short and light-coloured proboscis which has a long tip-region with a great number of club-shaped sensilla styloconica. Densely arranged, these sensilla form a flat brush located laterally from the openings into the food canal on the dorsal side of the tip-region. Among the non-flower-visiting species, a second type of proboscis was found in fruit-feeding Charaxinae the stout tip-region of which is equipped with more widely spaced sensilla styloconica. The investigated flower-visiting Heliconiinae, Nymphalinae, Satyrinae, Danainae and Ithomiinae are characterized by a slender, darker-coloured proboscis with a rather short tip-region bearing fewer sensilla styloconica in a loose arrangement. Discriminant analysis revealed that the tip-region length, the number of sensilla styloconica and the relative proboscis length are the most important discriminating variables between the flower-visiting and the non-flower-visiting species. The proboscis morphology of nymphalid butterflies corresponds with certain feeding habits and allow us to make predictions on their food preferences. The ‘brush-tipped’ proboscis seems to have a functional role in the accumulation of fluid and the uptake of liquid from wet surfaces such as rotting fruits or tree sap. We conclude from the phylogeny of the examined taxa that this derived proboscis tip morphology evolved several times independently as an adaptation to the exploitation of new food resources.
Broad versus narrow auditory tuning and corresponding bat-evasive flight behaviour in praying mantids
- Jeffrey D. Triblehorn, David D. Yager
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- 17 May 2001, pp. 27-40
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Most praying mantids possess a single tympanal ear located in the ventral midline between the metathoracic legs. The auditory system is generally most sensitive to ultrasound in the 25–50 kHz range. Flying males exhibit a short-latency, stereotyped, multi-component response to ultrasound that allows them to escape from attacking bats. This study describes a small subset of species that differs in three major respects from the majority of mantis species: (1) their auditory tuning is 1.5–2 times broader; (2) they are sensitive to frequencies above 60 kHz (up to 130 kHz in some species) with thresholds as low or lower than at 25–50 kHz; (3) the behavioural response of the broadly tuned (BT) species includes 10–50 times more flight cessations and can be far less stereotyped, i.e. more ‘evitable’, than that of narrowly tuned (NT) species. However, BT species do not differ from NT species in overall sensitivity. Two species from one subfamily, the Amelinae (family Mantidae), stand out because they are among the least sensitive of any hearing mantids so far tested. Although the two amelines differ from one another in tuning curve shape, they are both more broadly tuned than most mantids. The occurrence of BT species does not follow any obvious phylogenetic pattern; they are patchily distributed among the mantis families, and both BT and NT species can be found in the same subfamily or tribe. We suggest that BT species are responding to a shared ecological pressure. Based on their tuning, the nature of their behavioural response, and their geographic distribution, we hypothesize that high duty cycle (HDC) bats (Rhinolophidae and Hipposideridae) pose a special danger to BT mantids in addition to the threat that all flying mantids face from the more common and widely distributed low duty cycle (LDC) bats.
Implications of limb bone scaling, curvature and eccentricity in mammals and non-avian dinosaurs
- Matthew T. Carrano
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- 17 May 2001, pp. 41-55
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Current theories of locomotor biomechanics are based largely on observations of extant terrestrial mammals. However, extant mammals are limited with respect to certain aspects of terrestrial locomotion, and this constraint has confounded interpretations of limb design in this group. Dinosaurs include a wide array of large and small bipeds, record several transitions between bipedalism and quadrupedalism, and show a unique covariation of cursoriality and body size. Thus, the wider applications of biomechanical theories may be tested by applying them to the limb bones of dinosaurs. A broad examination of hindlimb and forelimb bone scaling patterns in dinosaurs and mammals reveals several general similarities that provide insight into the general constraints acting on terrestrial locomotion, particularly in animals with parasagittally oriented limbs. Most limb bones scale with negative allometry in these two groups, and larger taxa tend to scale more negatively than smaller forms. However, the strongly negative scaling of large mammals is mostly restricted to ungulates, whose unusually short femora may be the result of constraints of cursoriality at large body sizes. Bipedal and quadrupedal dinosaurs scale very similarly, with most differences apparently resulting from size rather than posture. Bone curvature tends to decrease with increasing body size, while femoral midshaft eccentricity tends to increase. Femoral midshaft eccentricity is explained as a general adaptation to mediolateral bending on parasagittal limb bones. These trends are more pronounced in dinosaurs than mammals; additional morphological constraints present in the dinosaurian hindlimb may contribute to this distinction.
Modulation of the adrenocortical stress response in marine turtles (Cheloniidae): evidence for a hormonal tactic maximizing maternal reproductive investment
- Tim S. Jessop
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- 17 May 2001, pp. 57-65
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The relationships between reproductive condition, level of reproductive investment and adrenocortical modulation to capture stress in marine turtles form the basis of this study. When subjected to either capture or ecological stressors, nesting marine turtles have demonstrated adrenocortical responses that are both small in magnitude, and slow in responsiveness. These observations were further investigated to determine whether this minimal stress response was a physiological strategy to maximize reproductive investment in adult green Chelonia mydas and hawksbill Eretmochelys imbricata turtles. Female green and hawksbill turtles exhibited a decrease in adrenocortical responsiveness with progressive reproductive condition. Breeding turtles exhibited most suppression of their adrenocortical response to capture compared to both non-breeding and pre-breeding female counterparts. Nesting green turtles maintained a suppressed adrenocortical response to capture throughout the nesting season despite decreased reproductive investment. In contrast, male green and hawksbill turtles were less able to modulate their corticosterone (B) response to acute capture stress. During breeding, male turtles possessed significantly greater adrenocortical responses to capture than females. These results could indicate that the large reproductive investment necessary for female marine turtle reproduction might underlie the marked decrease in adrenocortical responsiveness. This hormonal mechanism could function as one strategy by which female marine turtles maximize their current reproductive event, even though under certain situations this mechanism could entail costs to female survival.
Claw retraction and protraction in the Carnivora: the cheetah (Acinonyx jubatus) as an atypical felid
- Anthony P. Russell, Harold N. Bryant
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- 17 May 2001, pp. 67-76
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The cheetah Acinonyx jubatus is the most cursorial felid and has been described as somewhat dog-like in both the shape and the diminished degree of retraction of the claws. In this study we evaluate and investigate the osteological correlates associated with claw retraction in the cheetah through a comparison of the morphology of its middle phalanges with those of other felids and of the wolf Canis lupus. Compared to other felids, the middle phalanges of the cheetah have better-developed grooving of the distal articulatory facets in both the manus and pes, reduced to absent angulation to the distal articulatory facets in the inner and outer digits, less marked asymmetry of the shaft, and a mid-shaft cross-section that is less triangular and more circular. In all of these features, the morphology of the cheetah is intermediate between that of other felids and that of the wolf. The cheetah's distinctive morphology is autapomorphic within Felidae and similarities between the cheetah and the wolf are the result of convergence. Study of an ontogenetic series of specimens of the domestic cat suggests that the morphology of the cheetah can be explained, at least in part, as a product of heterochrony in which the development of the middle phalanx is truncated at an earlier stage than is typical of the adults of other felids. Some of the morphological differences in the middle phalanges of the cheetah can be associated with its distinctive hunting behaviour. The reduced manipulative capabilities of the forelimb associated with the evolution of cursorial adaptations seem to have limited the roles of the forepaws in both the subduing of prey and feeding.
Geographic variation in the Tete veld rat Aethomys ineptus (Rodentia: Muridae) from southern Africa
- C. T. Chimimba
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- 17 May 2001, pp. 77-89
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The Tete veld rat Aethomys ineptus Thomas & Wroughton, 1908 is a newly recognized, widely distributed species in southern Africa. Analysis of geographic variation among samples of A. ineptus from southern Africa across a more comprehensive geographical range than has previously been considered suggests that the species has a clinal pattern of variation in which overall cranial size was positively and significantly correlated with longitude. While the suggested clinal pattern of cranial size variation may be valid, the status of some operational taxonomic units, however, may require further refinement involving additional sampling as well as other systematic techniques, such as DNA analysis, cytogenetics and geometric morphometrics. These additional studies may have to include geographic information systems, step-wise multiple regression, and trend-surface analysis involving a wide range of environmental parameters to identify factors that may explain the nature and extent of the delineated pattern of geographic variation within A. ineptus from southern Africa. Consequently, the seven previously recognized subspecies recently assigned to A. ineptus in southern Africa (A. chrysophilus tzaneenensis Jameson, 1909; A. c. pretoriae Roberts, 1913; A. c. magalakuini Roberts, 1926; A. c. capricornis Roberts, 1926; A. c. tongensis Roberts, 1931; A. c. fouriei Roberts, 1946; and A. c. harei Roberts, 1946) are only provisionally synonymized.
The status of Nathusius' pipistrelle (Pipistrellus nathusii Keyserling & Blasius, 1839) in the British Isles
- J. M. Russ, A. M. Hutson, W. I. Montgomery, P. A. Racey, J. R. Speakman
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- 17 May 2001, pp. 91-100
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There are now 91 records of individual Nathusius' pipistrelle Pipistrellus nathusii examined ‘in the hand’ in the U.K., and bat detector records from a further 36 localities in Britain and Ireland. These records are distributed throughout all months of the year with clear peaks in spring and autumn suggesting migratory movements into and out of the British Isles in autumn and spring, respectively. Three maternity colonies have been located and the species must now also be regarded as a resident breeding species in Britain and Ireland.
Environmental conditions in burrows of two species of African mole-rat, Georhychus capensis and Cryptomys damarensis
- T. J. Roper, N. C. Bennett, L. Conradt, A. J. Molteno
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- 17 May 2001, pp. 101-107
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Temperature and respiratory gas (CO2 and O2) concentrations were measured in the foraging tunnels of burrows naturally inhabited by two species of southern African mole-rats, the Cape mole-rat Georhychus capensis and the Damaraland mole-rat Cryptomys damarensis. Both species are completely fossorial and inhabit closed burrow systems. Tunnels of G. capensis burrows had a mean diameter of 8.7 cm and a depth, measured to the roof of the tunnel, of 6.2 cm; those of C. damarensis had a mean diameter of 6.5 cm and depth of 40 cm. In both species, the mean concentration of CO2 was higher, and mean concentration of O2 lower, in burrows than in the surrounding soil or in ambient air. Mean and minimum values of O2 were 20.4% and 19.8%, respectively, in G. capensis and 20.4% and 19.9% in C. damarensis; mean and maximum values of CO2 were 0.4% and 1.2% in G. capensis and 0.4% and 6.0% in C. damarensis. Temperature varied between 18.5 and 24.2 °C in burrows of G. capensis by comparison with an ambient range of 16.9 to 26.8 °C; and from 19.6 to 29.3 °C in burrows of C. damarensis by comparison with an ambient range of 8.6 to 30.8 °C. Thus a burrowing habit seems to offer both species protection from extremes of temperature without entailing the cost of a grossly abnormal respiratory environment. From a review of the relevant literature, we conclude that average concentrations of CO2 and O2 in mammalian burrows often do not differ greatly from ambient values. However, more work is needed to determine the respiratory gas concentrations in the immediate vicinity of active, burrowing animals.
Sex discrimination and roostmate recognition by olfactory cues in the African bats, Mops condylurus and Chaerephon pumilus (Chiroptera: Molossidae)
- Sylvie Bouchard
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- 17 May 2001, pp. 109-117
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The ability of two species of African insectivorous bats (Angola free-tailed Mops condylurus and little free-tailed Chaerephon pumilus) to distinguish between males and females and roostmates from strangers in scent-choice experiments was tested. Both sexes of M. condylurus and male C. pumilus discriminated between sexes based on odours collected from the interaural and muzzle glandular areas, whereas female C. pumilus did not show any preference in either trials. Female M. condylurus from intermediate sized colonies (c. 200–600 individuals) distinguished female roostmates from strangers. There is some indication that roostmate recognition may vary inversely with the colony size of the test-subject suggesting that recognition is individually based, but further studies are necessary to determine if this is so. Histological work revealed that the interaural and muzzle area contain sebaceous glands and that the quantity of the glandular tissue is sexually dimorphic in both species for the interaural area, with males having more tissue, but not for the muzzle area. The presence of osmetrichia using SEM was also observed in the interaural area of both sexes of M. condylurus and in male C. pumilus. Their presence and association with sebaceous glands, as well as the results of the scent-choice experiments are indirect evidences of use of chemical signals, possibly pheromones, by these bats.
Diet, activity patterns, foraging movement and responses to deforestation of the aquatic tenrec Limnogale mergulus (Lipotyphla: Tenrecidae) in eastern Madagascar
- Jonathan P. Benstead, Kevin H. Barnes, Catherine M. Pringle
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- 17 May 2001, pp. 119-129
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The aquatic or web-footed tenrec Limnogale mergulus is a semi-aquatic lipotyphlan insectivore known only from stream habitats of eastern Madagascar. Limnogale is considered a high conservation priority because of its rarity, suspected vulnerability to habitat degradation, and unique ecological niche on the island. However, its ecology and behaviour remain poorly understood. Quantitative faecal analysis and radio-tracking were used to study the diet and foraging activity of Limnogale in eastern Madagascar. Faecal pellet counts along forest and zero-canopy streams were also conducted to examine the response of aquatic tenrec populations to catchment deforestation. Faecal analysis indicated that the diet of Limnogale consists mainly of larval and adult aquatic insects, larval anurans and crayfishes. The most important prey were Ephemeroptera, Odonata and Trichoptera larvae. Diets did not differ substantially between forest and zero-canopy streams. Radio-tracking of two individuals indicated that Limnogale is strictly nocturnal and remains in streamside burrows during daylight. Nocturnal movement was restricted solely to stream channels and consisted of active foraging by swimming and diving. Distance travelled per night ranged from 200 to 1550 m along the stream channel (means 1067 and 860 m, respectively). The total lengths of stream channel used by the two aquatic tenrecs during each radio-tracking study were 1160 and 505 m, respectively. Faecal pellet counts along forest and zero-canopy streams suggested that Limnogale was at least as abundant in zero-canopy streams. This finding suggests that Limnogale is not an obligate forest species; however, it preys on benthic communities that are extremely vulnerable to sedimentation. Control of excessive sedimentation and maintenance of healthy benthic communities are essential to Limnogale conservation. We include an updated list of known sites for Limnogale and recommend the use of faecal pellet surveys to assess the current distribution of the species.
Diet of the maned wolf, Chrysocyon brachyurus (Mammalia: Canidae), during wet and dry seasons at Ibitipoca State Park, Brazil
- M. Aragona, E. Z. F. Setz
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- 17 May 2001, pp. 131-136
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Analysis of 141 scats of maned wolf Chrysocyon brachyurus collected in a region of upland forest and meadows of south-eastern Brazil yielded 351 food items in the wet season (60 scats) and 407 in the dry season (81 scats). Scarabaeidae and rodents were the most frequent animal food in both seasons, complemented by birds in the wet season and unidentified mammals in the dry season. Seeds revealed Solanum lycocarpum to be the most frequent plant food in the dry season and an Annonaceae and a Cactaceae the most frequent in the wet season. A total of 33 seed morphospecies were retrieved. Although our results reveal some shared and some divergent trends from dietary studies undertaken in savanna (‘cerrado’) areas, we found a very high frequency of potentially harmful tourists' garbage. This highlights the necessity for better environmental education and confirms that the maned wolf is a generalist and opportunist omnivore.