Hystrix Africaeaustralis Research Articles

Wildlife resilience in an urban landscape: understanding land-use impacts in Cape Town

AbstractUrbanisation is rapidly transforming and fragmenting natural habitats, disrupting ecosystems and negatively impacting biodiversity. The City of Cape Town (CoCT) is situated in a global biodiversity hotspot, but sustained anthropogenic activities have resulted in the local extirpation of most medium and large mammals. A recent survey of mammals within urban protected areas of CoCT revealed that a few, mostly medium-sized generalist species, persist. It is uncertain which native mammal species, if any, inhabit the unprotected green belts and parks in suburban and urban areas of the city. A total of 37 camera trap sites were established along four transects for a period of four months between 31 January and 31 May 2022. A total of 12 terrestrial mammal species were detected, nine of which were wild native mammals and three domestic species. Most detections were in natural habitat followed by suburban, with urban areas having the lowest detection rate of wildlife. Single season hierarchical multi-species occupancy models revealed that tree cover had a significant positive effect on both community and individual species occupancy. Contrary to our predictions, neither human population density nor the extent of the impervious surface at sites significantly affected occupancy. Cape grysbok (Raphicerus melanotis) were significantly more likely to occur at sites with a higher proportion of impervious surfaces supporting other recent research, which showed this species together with water mongoose (Atilax paludinosus) and Cape porcupine (Hystrix africaeaustralis) are one of only a few native mammals that appear to persist and may even thrive in human-modified landscapes. Our findings underscore the complexity of urban biodiversity conservation and the species-specific responses to environmental factors, emphasising the importance of tree cover in urban wildlife management.

The impacts of Cape porcupines on woody plant mortality

AbstractIn terrestrial ecosystems, the activities of semi‐fossorial animals such as Cape porcupines have important landscape effects that may manifest in the dry season when the availability of above‐ground forage becomes limiting. We investigated the effects of foraging activities of Cape porcupines on savanna landscapes. We measured the size (surface area and depth) of foraging holes of porcupines located at the base of trees in the dry season in two mesic savanna sites at Roodeplaat Farm and Bisley Valley Nature Reserve in South Africa. We also recorded plant and animal activities inside the foraging holes for 3 months. The depth of foraging holes beneath small trees (Vachellia nilotica) was greater than depths beneath old trees (V. robusta and D. rotundifolia). This resulted in the subsequent death of most (>50%) small impacted trees in the dry season at Bisley. The surface area of foraging holes for older trees was greater than that for small trees and even greater for old holes. This study showed that porcupines kill trees or expose them to secondary attacks. The physical impacts of semi‐fossorial herbivores in savannas can be significant, with contributions to direct and indirect landscape transformation and restoration.

Facilitation of a free-roaming apex predator in working lands: evaluating factors that influence leopard spatial dynamics and prey availability in a South African biodiversity hotspot.

Apex predators ideally require vast intact spaces that support sufficient prey abundances to sustain them. In a developing world, however, it is becoming extremely difficult to maintain large enough areas to facilitate apex predators outside of protected regions. Free-roaming leopards (Panthera pardus) are the last remaining apex predator in the Greater Cape Floristic Region, South Africa, and face a multitude of threats attributable to competition for space and resources with humans. Using camera-trap data, we investigated the influence of anthropogenic land modification on leopards and the availability of their natural prey species in two contrasting communities-primarily protected (Cederberg) and agriculturally transformed (Piketberg). Potential prey species composition and diversity were determined, to indicate prey availability in each region. Factors influencing spatial utilisation by leopards and their main prey species were also assessed. Estimated potential prey species richness (Cederberg = 27, Piketberg = 26) and diversity indices (Cederberg-H' = 2.64, Ds = 0.90; Piketberg-H' = 2.46, Ds = 0.89), supported by both the Jaccard's Index (J = 0.73) and Sørensen's Coefficient (CC = 0.85), suggested high levels of similarity across the two regions. Main leopard prey species were present in both regions, but their relative abundances differed. Grey rhebok, klipspringer, and rock hyrax were more abundant in the Cederberg, while Cape grysbok, Cape porcupine, chacma baboon, and common duiker were more abundant in Piketberg. Leopards persisted across the agriculturally transformed landscape despite these differences. Occupancy modelling revealed that the spatial dynamics of leopards differed between the two regions, except for both populations preferring areas further away from human habitation. Overall, anthropogenic factors played a greater role in affecting spatial utilisation by leopards and their main prey species in the transformed region, whereas environmental factors had a stronger influence in the protected region. We argue that greater utilisation of alternative main prey species to those preferred in the protected region, including livestock, likely facilitates the persistence of leopards in the transformed region, and believe that this has further implications for human-wildlife conflict. Our study provides a baseline understanding of the potential direct and indirect impacts of agricultural landscape transformation on the behaviour of leopards and shows that heavily modified lands have the potential to facilitate mammalian diversity, including apex predators. We iterate that conservation measures for apex predators should be prioritised where they are present on working lands, and encourage the collaborative development of customised, cost-effective, multi-species conflict management approaches that facilitate coexistence.

Demonstrating a measurement protocol for studying comparative whisker movements with implications for the evolution of behaviour

BackgroundStudying natural, complex behaviours over a range of different species provides insights into the evolution of the brain and behaviour. Whisker movements reveal complex behaviours; however, there does not yet exist a protocol that is able to capture whisker movements and behaviours in a range of different species. New methodWe develop a new protocol and make recommendations for measuring comparative whisker movements and behaviours. Using two set-ups – an enclosure camera set-up and a high-speed video set-up - we capture and measure the whisker movements of sixteen different captive mammal species from four different animal collections. ResultsWe demonstrate the ability to describe whisker movements and behaviours across a wide range of mammalian species. We describe whisker movements in European hedgehog, Cape porcupine, domestic rabbit, domestic ferret, weasel, European otter and red fox for the first time. We observe whisker movements in all the species we tested, although movement, positions and behaviours vary in a species-specific way. Comparison with existing method(s)The high-speed video set-up is based on the protocols of previous studies. The addition of an enclosure video set-up is entirely new, and allows us to include more species, especially large and shy species that cannot be moved into a high-speed filming arena. ConclusionsWe make recommendations for comparative whisker behaviour studies, particularly incorporating individual and species-specific considerations. We believe that flexible, comparative behavioural protocols have wide-ranging applications, specifically to better understand links between the brain and complex behaviours.

The Thorny Issue of African Porcupines: a New Mandible of Hystrix makapanensis from Olduvai Gorge (Tanzania) and Rediagnosis of the Species.

Several porcupine taxa are reported from the middle Miocene to the early Holocene in the Old World. Among these, five species of the subfamily Hystricinae occurred in Africa approximately in the last 6 Ma: the extinct Hystrix makapanensis, Hystrix leakeyi, and Xenohystrix crassidens and the still living Hystrix africaeaustralis and Hystrix cristata. The large-sized H. makapanensis is reported from numerous sites in East and South Africa between the early Pliocene and Early Pleistocene. In this paper, we describe a new mandible of H. makapanensis from the world-renowned Tanzanian paleontological and archeological site of Olduvai Gorge (HWK West; lowermost Bed II; ca. 1.8–1.7 Ma). The discovery of the new mandible triggered a comprehensive review of the entire African record of H. makapanensis. In particular, we describe or re-analyze the samples from South Africa (Makapansgat Limeworks, Gondolin, Kromdraai, Swartkrans, and Sterkfontein), Tanzania (Olduvai and Laetoli), Ethiopia (Omo Shungura and Hadar), and Kenya (Chemeron), enriching the quantity of specimens confidently referable to this species and above all improving the information on its craniodental anatomy. On this basis, we: (1) propose an emended diagnosis of H. makapanensis; (2) point out the morphological and biometric differences between H. makapanensis and other African Hystricinae (also in terms of body mass); and (3) broaden the knowledge on the geographical and chronological distribution of this extinct species.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10914-021-09588-z.

Utilisation of Woody Plants by the Cape Porcupine in Mesic Savannas in South Africa.

Herbivory plays a fundamental role in determining the structure of savannas. The impacts of small and medium-sized mammalian herbivores on trees in savannas remain poorly understood because most research attention focuses on large herbivores such as elephants whose destructive effects on trees can be pervasive at landscape scales. On the other hand, feeding activities of generalist herbivores such as Cape porcupines on woody plants can lead to tree mortality. This study investigated the utilisation of woody plants by the Cape porcupine in three mesic savanna sites in South Africa. We determined the woody plant diet of the porcupine for the early and late dry seasons at Roodeplaat Farm in Gauteng Province, and at Goss Game Farm and Bisley Valley Nature Reserve in KwaZulu-Natal Province. Thirty and twenty randomly located quadrats (30 m × 30 m) were laid at Roodeplaat and Goss, respectively, while 10 smaller quadrats (10 m × 10 m) were laid at Bisley. We measured stem diameter and the length and width of bark scars made by porcupines on stems of woody plants. We collected ten dung samples from each study site in the wet and dry seasons for quantification of woody material in porcupine diet. Porcupine foraging behaviour impacted different tree species at each site: Vachellia robusta at Roodeplaat, Spirostachys africana at Goss and Vachellia nilotica at Bisley. Each of these trees was dominant at each site. More scarring and tree mortality were recorded at Bisley with almost 70% tree sapling mortality occurring on trees that porcupine fed on. The size of bark scars was greater at Goss (P < 0.01) than at Roodeplaat and Bisley, which were similar. The area of bark damage on S. africana trees differed significantly by stem diameter size class (P = 0.007) and was greater for small stems (size class < 7.1 cm) than the larger stems (size classes 7.1-14 cm and 14.1-21). For all the study sites, dung samples revealed that woody material contributed over 80% of the porcupine diet during the dry season, but was lower at 35% during the wet season for Roodeplaat, although it was consistently high for Bisley at 79%. Porcupine foraging activities substantially contributed to tree mortality at each site. We posit that porcupine induced mortality on dominant tree species at each site may contribute to structural heterogeneity in woody plant vegetation in mesic savannas.

Human–wildlife conflict in Mhokwe Ward, Mbire District, North‐East Zimbabwe

AbstractThis research investigates the economic and social aspects of human–wildlife conflict (HWC) in Mhokwe, Mbire district, Zimbabwe. Data were collected through key informant interviews and a questionnaire survey. Most households in Mhokwe rely on crop and livestock production, and hence, HWC is an important factor affecting livelihoods. More than 60% of respondents experienced problems with lions (Panthera leo Linnaeus), spotted hyaenas (Crocuta crocuta Erxleben), armoured bush crickets (Acanthoplus speiseri Brancsik) and quelea birds (Quelea quelea Reichenbach). Other problem animals included elephant (Loxodonta africana Blumenbach), vervet monkey (Chlorocebus pygerythrus Cuvier), kudu (Tragelaphus strepsiceros Pallas), chacma baboon (Papio ursinus Kerr), bushpig (Potamochoerus porcus Linnaeus) and common duiker (Sylvicapra grimmia Linnaeus). Few incidences of conflicts were reported for hippopotamus (Hippopotamus amphibius Linnaeus), side‐striped jackal (Canis adustus Sundevall), porcupine (Hystrix africaeaustralis Peters), nile crocodile (Crocodylus niloticus Laurenti), African wild cat (Felis lybica Forster), African python (Python sebae Gmelin) and guinea fowl (Numida meleagris Linnaeus). Livestock and crop losses were US$45,285 and US$57,541 in 2013 and 2014, respectively. Despite the losses, most respondents had positive attitudes towards wildlife. Construction of strong kraals and implementation of integrated pest management (IPM) can contribute to conflict reduction.

Scavenger activity in a peri-urban agricultural setting in the Highveld of South Africa.

Scavenging animals often scatter skeletal remains of forensic interest and cause scavenging damage. This study aimed to identify scavenging animals in the peri-urban agricultural Highveld of South Africa, describe their scattering patterns, and the damage they cause to bone. Ten pig carcasses (Sus scrofa domesticus) (40-80kg) were placed at the University of Pretoria's Mierjie Le Roux Experimental Farm (Highveld) in summer and winter. Motion-activated cameras recorded the scavenging. Scavenger species were identified and their behaviors, scattering pattern, and the damage they cause to bone were described. Scavenging was primarily by black-backed jackals; however, mongooses (slender, yellow, and water mongoose), Cape porcupine, and honey badger were also active. Remains were commonly scattered in two directions by jackals. The distance of scattering was heavily influenced by fencing. The remains were scattered within a maximum radius of 73.7m. The remains were scavenged and skeletonized faster in summer. Jackals caused minimal damage to bone, isolated to superficial, nonspecific scores, furrows, and punctures. A few mongoose bone alterations were present as jagged gnaw marks on the angle of the mandible and gnawing of the vertebral spinous process. Cape porcupine bone damage included gnaw marks on the condyle of a femur and head of humerus, and destruction of the proximal and distal ends of a tibia. The described scattering pattern and bone modification patterns will assist in the recovery and analysis of scavenged remains found in peri-urban agricultural areas in South Africa.

Evidence of scavenging behaviour in crested porcupine

The vegetarian diet of many herbivorous mammals is supplemented with proteins of animal origin, especially in young individuals and in breeding females, to provide key proteins necessary for both growth and breeding. Among porcupine species, only the Cape porcupine (Hystrix africaeaustralis) has been observed to consume carrion flesh. From June to August 2019, a pigeon carcass was placed together with corn in 7 study settlements and near 2 monitored capture-traps, in order to assess the carrion flesh feeding habits of the crested porcupine (Hystrix cristata). Scavenging behaviour was recorded on four occasions. All the recorded individuals were adults and at least one was female. This demonstrates that the crested porcupine occasionally does eat flesh. Such evidence raises important questions concerning the relationship between feeding habits and the physiological needs of this herbivorous rodent.

Habitat selection of Cape porcupines in a farmland-suburban context in KwaZulu-Natal, South Africa

Cape porcupines (Hystrix africaeaustralis) have a wide geographic distribution throughout southern Africa and have a wide ecological tolerance of many terrestrial habitats, including those within human-altered landscapes. Due to their adaptability within anthropogenic landscapes, knowledge of their spatial behaviour will provide fundamental information about this species. With the aid of telemetry data (July 2016–January 2017) from 11 Cape porcupines, we investigated their habitat selection in a farmland-suburban context in KwaZulu-Natal, South Africa. Two levels of selection were determined, 1) at the landscape area scale (2nd order of selection) and 2) at the home range scale (3rd order of selection). Our results showed a variation in their habitat selection at the two spatial scales. Although all Cape porcupines selected the forest with bushland habitat at the landscape scale, we observed a few individuals selecting the residential and grassland habitats or used these habitat types in proportion to their availability, at the home range scale. Agricultural areas (farmlands and timber plantations) were used by Cape porcupines, but were not selected. In suburban areas, the availability of naturally woody vegetation appeared to be the main driver of the species persistence within these landscapes. Also, we addressed possible human-porcupine conflict and provide management recommendations for cultivated farmlands and suburban gardens, where the species appear to be most conflict-prone.

Traditional medicinal animal use by Xhosa and Sotho communities in the Western Cape Province, South Africa

BackgroundThe use of animals and animal-derived materials in traditional medicine constitutes an important part of the belief systems of indigenous African cultures. It is believed to be rapidly expanding in South Africa, where traditional healers are estimated to outnumber western doctors by 2000:1 in some areas, with an overall clientele consisting of 60–80% of South African citizens. Despite concerns about the impact of the trade in traditional medicine on biodiversity, there has been only limited research on this topic in South Africa.MethodsTraditional Xhosa and Sotho healers operating from impoverished, rural communities in the Boland Region of the Western Cape Province were consulted to provide a comprehensive inventory of the number and frequency of animals used and sold. Species richness estimators, diversity indices, and a relative cultural importance (RCI) index were used to highlight species of concern and assess market dynamics.ResultsA total of 26 broad use categories for 12 types of animal parts or products from 71 species or morphospecies were recorded. The most commonly sold items were skin pieces, oil or fat, and bones. Results showed that leopard, chacma baboon, Cape porcupine, monitor lizard species, puff adder, African rock python, and black-backed jackal were the species most used in the traditional medicinal trade.ConclusionsThis study extends existing knowledge on the trade of animals in South African healing practices and provides the first attempt in the Western Cape to quantify wildlife use for cultural traditions. The results have relevance for setting conservation priorities and may assist in effective policy development inclusive of ecological sustainability priorities, as well as cultural demands.

Predation of porcupine Hystrix africaeaustralis in the den by honey badger Mellivora capensis

A porcupine (Hystrix africaeaustralis) den was placed under observation by camera trap, and subsequently a honey badger (Mellivora capensis) was recorded raiding the den to prey on the young porcupines inside.

Home ranges of Cape porcupines on farmlands, peri-urban and suburban areas in KwaZulu-Natal, South Africa

Cape porcupines, Hystrix africaeaustralis, are one of the South African mammalian species that are increasing their distribution range and abundance with anthropogenic changing land-use. Knowledge of the home range of this species can provide important ecological information and explain their ability to persist in a range of land-use types. We investigated the home ranges of 15 radio-tagged Cape porcupines on farmlands, peri-urban and suburban areas in KwaZulu-Natal, South Africa. Using the 95% Kernel Density Estimator (KDE), Cape porcupines had an overall estimated mean home range of 39.37 ± 6.33 ha (n = 9) which ranged from 13.19 to 67.19 ha. When compared with other Hystrix species, Cape porcupines had the lowest estimated home range size. Individuals on farmlands had the smallest mean estimated home range area (24.57 ha), relative to peri-urban (34.61 ha) and suburban (45.18 ha) sites. Variation in the home range sizes of Cape porcupines with differing anthropogenic land-use type showed their behavioural flexibility in response to habitat heterogeneity and forage availability in each. Our results suggest that Cape porcupine ranging ecology is influenced by food resource distribution and availability in various land-use types.

Forest habitats in a mixed urban-agriculture mosaic landscape: patterns of mammal occupancy

Conservation planning for biodiversity within anthropogenic landscapes is crucial given the rate of habitat conversion and human population growth. Investigating anthropogenic impacts on the persistence of biodiversity is key to management decision-making. We investigated the influence of protected areas (PAs), agriculture and urbanisation on the occupancy of mammal communities in an anthropogenic matrix containing indigenous forest fragments of the Coastal Belt of southern KwaZulu-Natal, South Africa. We integrated camera-trap mammal data, land-use and human population density within occupancy models, and compared occupancy of individual species across the land-use mosaic. We modelled occupancy of seven mammal species with sufficient naive occupancy (> 0.20, range 0.25–0.87). The occupancy of Philantomba monticola was positively influenced by human population size and was higher within urban areas compared with PAs. Although human population size positively affected Hystrix africaeaustralis occupancy, it along with Atilax paludinosus had a lower occupancy within urban areas. Tragelaphus scriptus and Potamochoerus larvatus overall had higher and Sylvicapra grimmia had lower occupancies within PAs. Species were variable in their response to the anthropogenic changes in the landscape. For example, occupancy of P. monticola was low within PAs but high in areas where change in land ownership and loss of habitat are threats. For other species, it appeared that the density of infrastructure of the urban landscape, rather than human population density, affected them negatively. However, seasonal differences within different management regimes also provided context-specific influences on occupancy and detectability. We emphasize the importance of natural vegetation patches within anthropogenic landscapes for maintaining native fauna, whilst stressing the value of temporally replicated, multi-species, regional-scale studies when making conservation decisions.

Orchiectomy of a Cape porcupine (Hystrix africaeaustralis)

A Cape porcupine (Hystrix africaeaustralis) was presented for surgical castration to prevent inbreeding within the family group. A literature review found limited information on relevant anatomy and surgical approach, with...

The importance of microhabitat structure in maintaining forest mammal diversity in a mixed land-use mosaic

The Indian Ocean Coastal Belt (IOCB) of South Africa is a natural forest-grassland mosaic, nested within an anthropogenic, mixed land-use matrix. Given the ongoing threat of agricultural expansion and urbanisation, we assessed the value of a buffer habitat (Coastal dense bush) for conserving forest species. We investigated the influence of microhabitat complexity on mammal communities within forest and dense bush habitats, using occupancy modelling. We found vertical stratification gradients as observed in studies of tropical forest chronosequence, i.e. increased foliage density in lower habitat layers and decreased foliage density in higher habitat layers for dense bush, and vice versa for forest. Structural composition suggests that dense bush is within a successional stage of secondary forest regeneration. Bushbuck (Tragelaphus scriptus) occupancy was higher in forest than dense bush, while the opposite was true for blue duiker (Philantomba monticola). Large-spotted genet (Genetta tigrina), Cape porcupine (Hystrix africaeaustralis) and marsh mongoose (Atilax paludinosus) occupancy remained constant between habitats. Grey duiker (Sylvicapra grimmia) occupancy varied greatly between dense bush (0.48 ± 0.01) and forest (0.16 ± 0.01). Dense bush appeared to maintain natural forest assemblages, and may play a crucial role in buffering IOCB forest patches, given their highly-restricted distribution. However, dense bush habitats have no protection status, but play a role in the conservation of forest plants and animals. Therefore, we advocate the inclusion of dense bush habitats in conservation networks focused on forests.

Digestive parameters and energy assimilation of Cape porcupine on economically important crops

To better understand how Cape porcupines are able to successfully occupy many agricultural lands, we studied their digestive parameters and energy assimilation when fed three economically important agricultural crops (potatoes [Solanum tuberosum], sweet potatoes [Ipomoea batatas] and butternut [Juglans cinerea]). Daily food intake, daily gross energy intake, daily faecal energy loss, daily energy assimilated, daily water intake and apparent assimilation efficiency were calculated for each porcupine and for each diet trial. Cape porcupines maintained body mass on all three experimental diets and energy intake ranged from 3 002.36 kJ kg−1 d−1 (potato) to 4 499.00 kJ kg−1 d−1 (sweet potato). The moisture content in each experimental diet was relatively high (>60%) and preformed water intake of winter acclimated Cape porcupines ranged from 60 ml kg−1 d−1 (potato) to 100 ml kg−1 d−1 (sweet potato). Assimilation efficiencies were high (>85%) on all three diets. Cape porcupines ingested c. 1.5–2.7 kg of each crop daily, translating to potentially large economic impacts on farmers. Knowledge and understanding of Cape porcupine food intake and dietary requirements give insight to their potential impact on commercial crops. This may aid in developing management and conservation strategies needed to manage this human–wildlife conflict.

Penetration ability of echidna spines and porcupine quills

The structure and function of 10 echidna (Tachyglossus aculeatus) spines and 10 cape porcupine (Hystrix africaeaustralis) quills were compared with regard to their ability to penetrate a mammalian muscle tissue analogue (10% gelatine). All specimens showed a significant correlation between the load applied and the depth of penetration into the gel. There was no significant difference between the penetration ability of the echidna spines and the porcupine quills despite the finding that quills had a significantly smaller angle at the tip of the spine (opening angle). The penetration ability of echidna spines was inversely related to the opening angle whereas there was no such correlation in porcupine quills. These findings are discussed in relation to the different response of these two species to possible predators.

Field relationships, petrology, age, and tectonic setting of the Late Cambrian–Ordovician West Barneys River Plutonic Suite, southern Antigonish Highlands, Nova Scotia, Canada

The West Barneys River Plutonic Suite consists of gabbro, syenite-monzonite, alkali-feldspar syenite to quartz alkali-feldspar syenite, and alkali-feldspar granite outcropping in an area of ∼100 km2 in the southern Antigonish Highlands. Magma mixing and mingling textures indicate a comagmatic relationship between some of the mafic and intermediate–felsic lithologies. However, nine U–Pb (zircon) ages, three by thermal ionization mass spectrometry (TIMS) and six by laser-ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS), from the West Barneys River suite and the lithologically similar Cape Porcupine Complex located 60 km to the east range from ca. 495 to 460 Ma, indicating that emplacement occurred over a significant span of time. Intermediate to felsic rocks consist mainly of perthitic K-feldspar and variable amounts of quartz; interstitial granophyre is present in some samples, consistent with shallow emplacement. Mafic phases are Fe-rich amphibole and clinopyroxene, and in some units, fayalite. Intermediate and felsic samples have chemical characteristics of within-plate ferroan A-type granitoid rocks. Gabbroic rocks consist of plagioclase (oligoclase–labradorite) and augite/diopside with less abundant orthopyroxene, olivine, biotite, and ilmenite/magnetite. Their chemical compositions are transitional from tholeiitic to alkalic and characteristic of continental within-plate mafic rocks. The εNd values are similar in gabbroic, syenitic, and granitic samples, ranging between 0.9 and 4.9, consistent with a co-genetic origin for the mafic and intermediate/felsic components of the suite, and derivation from Avalonian subcontinental lithospheric mantle in an extensional environment.

The Cape Porcupine Complex, northern mainland Nova Scotia – no longer a geological orphan

The Cape Porcupine Complex west of the Strait of Canso in northern mainland Nova Scotia consists of mainly fault-bounded units of metasedimentary, metavolcanic, and granitoid rocks. A previously reported U-Pb (zircon) age of 610 ± 3 Ma from syenogranite combined with petrological characteristics indicates that some of the granitic rocks and possibly an associated body of leucodiorite are Late Neoproterozoic. In contrast, alkali-feldspar granite from a more extensive suite of quartz alkali-feldspar syenite/alkali-feldspar syenite, alkali-feldspar granite/syenogranite, and quartz alkali-feldspar leucosyenite with A-type characteristics yielded an early Ordovician age of 478 ± 3 Ma. Similar A-type chemical characteristics suggest that the metavolcanic unit may be the extrusive equivalent of the Ordovician suite.Similarities in age and petrological characteristics indicate that the Cape Porcupine Complex is linked to rock units in the Antigonish Highlands. The ca. 610 Ma granitic rocks are likely related to plutonic and volcanic rocks of similar age in the Antigonish Highlands interpreted to have formed at a continental margin subduction zone. In contrast the A-type syenitic and metavolcanic rocks are probably related to the compositionally similar West Barneys River plutonic suite and younger volcanic rocks formed in an extensional regime. Such rocks do not occur in adjacent Ganderia or Avalonia in Cape Breton Island or southern New Brunswick, further demonstrating the regional significance of the Canso Fault in tectonic reconstructions.RÉSUMÉSitué à l’ouest du détroit de Canso au nord de la partie continentale de la Nouvelle-Écosse, le complexe du cap Porcupine se compose principalement d’unités rocheuses métasédimentaires, métavolcaniques et de granitoïdes limitées par des failles. Une datation réalisée précédemment par la méthode U-Pb sur zircon et qui a établi un âge de 610 ± 3 Ma à partir du syénogranite et des caractéristiques pétrologiques indique qu’une partie des roches de granite et vraisemblablement un corps connexe de leucodiorite sont du Néoprotérozoïque tardif. Par contraste, du granite de feldspath alcalin d’une succession plus importante de syénite de feldspath alcalin quartzeux/syénite de feldspath alcalin, de granite de feldspath alcalin/syénogranite, et de leucosyénite de feldspath alcalin quartzeux présentant des caractéristiques de type A a produit un âge de l’Ordovicien précoce, soit environ 478 ± 3 Ma. Ces caractéristiques chimiques de type A analogues portent à croire que l’unité métavolcanique pourrait être l’équivalent extrusif de la succession de l’Ordovicien.Les similitudes de datation et les caractéristiques pétrologiques indiquent que le complexe du cap Porcupine est relié aux unités rocheuses des hautes-terres d’Antigonish. L’âge du granite, d’environ 640 Ma, se rapporterait vraisemblablement aux roches plutoniques et volcaniques de la même époque observées dans les hautes-terres d’Antigonish, dont on suppose qu’elles ont été formées dans une zone de subduction de la marge continentale. Par contraste, les roches métavolcaniques et syénitiques de type A sont probablement reliées par la similitude de leur composition au cortège plutonique et aux roches volcaniques plus jeunes de la rivière Barneys Ouest formées dans un milieu de distension. Ces roches ne sont pas présentes dans la partie adjacente de Ganderia ou d’Avalonia sur l’île du Cap-Breton ou dans le sud du Nouveau-Brunswick, ce qui tendrait à souligner encore plus l’importance régionale de la faille de Canso dans les reconstructions tectoniques.[Traduit par la redaction]