Canterbury spotted skink

Canterbury spotted skink
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Scincidae
Genus: Oligosoma
Species:
O. lineoocellatum
Binomial name
Oligosoma lineoocellatum
Dumeril, 1851
Distribution of the Canterbury spotted skink on a map of the South Island
  Known native range

Oligosoma lineoocellatum, commonly known as the Canterbury spotted skink, is one of a species complex of several related spotted skink species from New Zealand.[2]

Taxonomy

The Canterbury spotted skink Oligosoma lineoocellatum [3] is one of a species complex of several related spotted skink species in New Zealand.[2]

The four species within this complex are the Canterbury spotted skink O. lineoocellatum sensu stricto, the Mackenzie skink Oligosoma prasinum,[2] the Marlborough spotted skink Oligosoma elium,[2] and the Northern spotted skink Oligosoma kokowai.[2]

These species are very morphologically similar; however, are distinguished by their differences in geographic distribution and genetic differences.[2]

Identification

The Canterbury spotted skink is a large, eye-catching skink with a snout-vent length reaching up to 107mm.[4] Individuals typically have an olive-green, brown or brown-grey dorsal (upper side) surface with light and dark coloured spots (ocelli) which extend almost to the tail tip.[4][5] Some individuals have also been found to have light dorsolateral stripes stretching from above the eye to the beginning of the tail.[4][5] The lateral (side) surface exhibits a dark brown or brown-black lateral band with specks and white edges notched, extending from the front of the eyes to the tail tip.[4] A thin pale stripe runs beneath this, transitioning into intermittent patches of cream and dark brown on the lower side surface.[4][5] The ventral (underside) surface of the skink is grey in uniform, flushed with orange or pink, with a pale chin and throat covered in dark spots.[4][5] Individuals have dark brown eyes with an intact tail longer than the snout-vent length.[4] The Canterbury spotted skink has cream or grey soles on its feet with 21–25 subdigital lamellae (scales underneath fingers or toes).[4]

There are a several skinks that closely resemble the Canterbury spotted skink which can make it more challenging to identify them. The Mackenzie skink and Marlborough spotted skink are similar species; however, this is differentiated by the Canterbury spotted skink usually having more than 24 subdigital lamellae and the ocelli markings on the dorsal surface running down the tail.[4] The uniformly grey underside, the greater ratio of snout-vent length to head-width and the different geographic locations differentiate the Canterbury spotted skink from the Northern spotted skink.[4] Members of the Oligosoma chloronoton[6] species complex (green skinks) also appear similar to the Canterbury spotted skink; however, the Canterbury spotted skink usually has more than 22 subdigital lamellae compared to the green skinks and features fewer anterior subocular scales (below the eyes) of similar sizes.[4]

Geographic distribution and habitat

The Canterbury spotted skink is an endemic species of skink only found in the Canterbury region of New Zealand.[4] This distribution spreads from Mount Grey in the north, Banks Peninsula in the east, and the Rangitata River in the south.[4][5] This species may also be seen further south in Canterbury.[4][5] O. lineoocellatum can be found in various environments including lowland, coastal, montane/subalpine and alpine.[4] These also vary in altitude from sea level up to 1400m.[7] In these environments, the Canterbury spotted skink has been found in a wide range of habitats. These are grasslands, rock piles, boulder and cobble beaches,[8][4][5] dune shrubland,[4][5] flaxland,[4][5] edges of forest [5] scree slopes, fellfields,[4][5] stony coasts and riverbeds,[4][5] herbfields,[5] and vinelands.[4]

Life cycle and phenology

The Canterbury spotted skink is diurnal[4][5] meaning it is active during the day. It is also heliothermic (gains heat from the sun) so spends a lot of time basking in the sun.[4] Mating occurs at the beginning of autumn[9] and females are viviparous (live bearing). Breeding occurs once per year with pregnancies lasting 4–5 months [10] ending between February and March.[4] The average clutch size (number of offspring produced) of 3.82 (+/-0.18).[11] The mating system of the Canterbury spotted skink is widely unknown.[12] Research has been done on Oligosoma grande[13] where observations suggested mating was polygynous (one male with multiple females)[14] However, genetic studies of this species found that over one breeding season, both males and females had more than one partner using a promiscuous mating system.[15]

Population modelling has been done on a population of the McCann’s skink Oligosoma maccanni,[16] at Kaitorete Spit in Canterbury.[17] This study categorised the different life stages of the skink based on their snout-vent-length (SVL). McCann’s skinks born within the same year have an SVL between 25-39mm, juveniles were between 40-48mm SVL, and adults had an SVL greater than 49mm, respectively.[18][19][17] For O. lineoocellatum, it has been assumed the age of maturity is 4 years, with a life expectancy of 10 years.[20] Monitored populations have shown an ongoing decline with a predicted decline of more than 70% over the next 10 years or three generations.[20]

Diet, prey and predators

Individuals of O. lineoocellatum display an active foraging behaviour meaning they are actively searching for prey instead of waiting for it to come to them.[21][22][23][11] The Canterbury spotted skink is omnivorous feeding on both plant and animal material.[4] A study found Oligochaeta (earthworms), Coleoptera (beetles), Hymenoptera (wasps and bees), Diplopoda (millipedes) and Lepidoptera (butterflies and moths) were the highest sources of prey for O. lineoocellatum.[11] Seeds and fruit were also found in their diet, but were present in a lower percent of stomachs of the skinks surveyed.[11] Other sources of food include nectar and smaller lizards including other Canterbury spotted skinks.[4] Although O. lineoocellatum is diurnal, the findings from the study show their main prey species are nocturnal suggesting they may also forage at night.[11]

In New Zealand, 50 species have been recorded predating on lizards with 51% of these being birds.[12] Introduced mammals such as rats, hedgehogs and cats are also major predators of lizards.[12]

Researchers have recorded multiple parasites on skinks within the spotted skink species complex.[2] However, they have not yet determined exactly with which skink species each parasite is associated.[2] These parasites recorded include trematodes: Dolichosaccus (Lecithopyge) leiolopismae,[24] Paradisomum pacificus, cestodes: Oochoristica novaezealandicae, nematodes: Parathelandros sp.; Skrjabinodon trimorphi and protozoans: Haemogregarina sp.[2]

Other information

The Canterbury spotted skink is classified as “threatened- nationally critical” under the New Zealand Threat Classification system.[20] Population estimates suggest there are between 1,000 – 5,000 mature individuals left and this is predicted to decline over three generations by 10-50%.[25] The biggest threats to the Canterbury spotted skink are invasive mammalian predators and habitat loss due to land use change.[2]

New Zealand lizards are important seed dispersers and can assist with dispersal in areas where fruigivorous (feeding on fruit) birds are not present.[26][27] Studies have also found that lizards can be effective pollinators.[28][29]

References

  1. ^ IUCN (2018-02-17). Oligosoma lineoocellatum: Hitchmough, R., van Winkel, D., Lettink, M. & Chapple, D.: The IUCN Red List of Threatened Species 2019: e.T120189599A120192619 (Report). International Union for Conservation of Nature. doi:10.2305/iucn.uk.2019-2.rlts.t120189599a120192619.en.
  2. ^ a b c d e f g h i j Melzer, S; Bell, T; Patterson, G. B. (3 August 2017). "Hidden conservation vulnerability within a cryptic species complex: taxonomic revision of the spotted skink (Oligosoma lineoocellatum; Reptilia: Scincidae) from New Zealand". Zootaxa. 4300 (3). doi:10.11646/zootaxa.4300.3.2.
  3. ^ Duméril, C; Duméril, A (1851). Catalogue methodique de la collection des reptiles. Paris: Gide and Baudry. p. 124.
  4. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z Van Winkel, D; Baling, M; Hitchmough, R (2018). Reptiles and Amphibians of New Zealand: A Field Guide. Auckland, New Zealand: Auckland University Press. ISBN 9781869409371.
  5. ^ a b c d e f g h i j k l m n Purdie, S (2022). A Naturalist’s Guide to the Reptiles & Amphibians of New Zealand. Oxford, England: John Beaufoy Publishing. ISBN 9781913679316.
  6. ^ Hardy, G. S. (1977). "The New Zealand Scincidae (Reptilia: Lacertilia); a taxonomic and zoogeographic study". New Zealand Journal of Zoology. 4 (3): 221–325. doi:10.1080/03014223.1977.9517956. ISSN 0301-4223.
  7. ^ Mark, A. F. (2012). Above the Treeline: a Nature Guide to Alpine New Zealand. Nelson, New Zealand: Craig Potton Publishing. ISBN 9781877517761.
  8. ^ Jewell, T (2008). A Photographic Guide to Reptiles & Amphibians of New Zealand. Auckland, New Zealand: New Holland Publishers (NZ) Ltd. ISBN 9781869662035.
  9. ^ Molinia, F. C.; Bell, T; Norbury, G; Cree, A; Gleeson, D.M. (2010). "Assisted breeding of skinks or how to teach a lizard old tricks!" (PDF). Herpetological Conservation and Biology. 5 (2): 311–319.
  10. ^ Cree, A; Hare, K. M. (2016), Chapple, David G. (ed.), "Reproduction and Life History of New Zealand Lizards", New Zealand Lizards, Cham: Springer International Publishing, pp. 169–206, doi:10.1007/978-3-319-41674-8_5, ISBN 978-3-319-41674-8, retrieved 2024-05-10
  11. ^ a b c d e Spencer, N. J.; Thomas, B. W.; Mason, R. F.; Dugdale, J. S. (1998). "Diet and life history variation in the sympatric lizards Oligosoma nigriplantare polychroma and Oligosoma lineoocellatum". New Zealand Journal of Zoology. 25: 457–463. doi:10.1080/03014223.1998.9518169. ISSN 0301-4223.
  12. ^ a b c Hare, K. M.; Chapple, D. G.; Towns, D. R.; van Winkel, D (2016), Chapple, D. G. (ed.), "The Ecology of New Zealand's Lizards", New Zealand Lizards, Cham: Springer International Publishing, pp. 133–168, doi:10.1007/978-3-319-41674-8_6, ISBN 978-3-319-41674-8, retrieved 2024-05-10
  13. ^ Gray, J. E. (1845). Catalogue of the Specimens of Lizards in the Collection of the British Museum. London: Edward Newman. p. 171.
  14. ^ Eifler, D. A.; Eifler, M. A. (1999). "Foraging behavior and spacing patterns of the lizard Oligosoma grande". Journal of Herpetology. 33 (4): 632–639. doi:10.2307/1565580. ISSN 0022-1511.
  15. ^ Berry, O. F. (2006-06-01). "Inbreeding and promiscuity in the endangered grand skink". Conservation Genetics. 7 (3): 427–437. doi:10.1007/s10592-005-9054-0. ISSN 1572-9737.
  16. ^ Patterson, G. B.; Daugherty, C.H. (1990). "Four new species and one new subspecies of skinks, genus Leiolopisma (Reptilia: Lacertilia: Scincidae) from New Zealand". Journal of the Royal Society of New Zealand. 20 (1): 65–84. doi:10.1080/03036758.1990.10426733. ISSN 0303-6758.
  17. ^ a b Lettink, M; Cree, A; Norbury, G; Seddon, P. J. (2008). Monitoring and restoration options for lizards on Kaitorete Spit, Canterbury. Wellington, New Zealand: Department of Conservation. ISBN 9780478145007.
  18. ^ Freeman, A (1997). "The conservation status of a coastal duneland lizard fauna at Kaitorete Spit, Canterbury, New Zealand". Herpetofauna. 27 (1): 25–30.
  19. ^ Lettink, M (2007). Adding to Nature: Can Artificial Retreats be Used to Monitor and Restore Lizard Populations? (Unpublished PhD thesis). Dunedin, New Zealand: University of Otago.
  20. ^ a b c Hitchmough, R; Barr, B; Knox, C; Lettink, M; Monks, J. M.; Patterson, G. B.; Reardon, J. T.; Van Winkel, D; Rolfe, J; Michel, P (2021). Conservation status of New Zealand reptiles, 2021 (New Zealand Threat Classification Series 35 ed.). Wellington, New Zealand: Department of Conservation. ISBN 978-1-7386283-0-8.
  21. ^ Patterson, G. B. (1985). "The Ecology and taxonomy of the common skink Leiolopisma nigriplantare maccanni in tussock grasslands in Otago".
  22. ^ Towns, D. R.; Daugherty, C. H.; Newman, D. G. (1985). "An overview of the ecological biogeography of the New Zealand lizards (Gekkonidae, Scincidae)". In Grigg, G; Shine, R; Ehmann, H (eds.). Biology of Australasian frogs and reptiles. Chipping Norton, New South Wales: Surrey Beatty, Chipping Norton, NSW, with Royal Zoological Society of NSW. pp. 107–115. ISBN 9780949324030.
  23. ^ East, K. T.; East, M. R.; Daugherty, C. H. (1995). "Ecological restoration and habitat relationships of reptiles on Stephens Island, New Zealand". New Zealand Journal of Zoology. 22 (3): 249–261. doi:10.1080/03014223.1995.9518040.
  24. ^ Allison, B; Blair, D (1987). "The genus Dolichosaccus (Platyhelminthes: Digenea) from amphibians and reptiles in New Zealand, with a description of Dolichosaccus (Lecithopyge) leiolopismae n. sp". New Zealand Journal of Zoology. 14 (3): 367–374. doi:10.1080/03014223.1987.10423007. ISSN 0301-4223.
  25. ^ Hitchmough, R; Barr, B; Lettink, M; Monks, J; Reardon, J; Tocher, M; Van Winkel, D; Rolfe, J (2016). Conservation status of New Zealand reptiles, 2015 (New Zealand Threat Classification Series 17 ed.). Wellington, New Zealand: Department of Conservation. ISBN 9781988514000.
  26. ^ Whitaker, A. H. (1987). "The roles of lizards in New Zealand plant reproductive strategies". New Zealand Journal of Botany. 25 (2): 315–328. doi:10.1080/0028825X.1987.10410078. ISSN 0028-825X.
  27. ^ Wotton, D. M.; Drake, D. R.; Powlesland, R. G.; Ladley, J. J. (2016). "The role of lizards as seed dispersers in New Zealand". Journal of the Royal Society of New Zealand. 46 (1): 40–65. doi:10.1080/03036758.2015.1108924. ISSN 0303-6758.
  28. ^ Traveset, A; Sáez, E (1997). "Pollination of Euphorbia dendroides by lizards and insects: Spatio-temporal variation in patterns of flower visitation". Oecologia. 111 (2): 241–248. doi:10.1007/PL00008816. ISSN 0029-8549.
  29. ^ Nyhagen, D. F.; Kragelund, C; Olesen, J. M.; Jones, C. G. (2001). "Insular interactions between lizards and flowers: flower visitation by an endemic Mauritian gecko". Journal of Tropical Ecology. 17 (5): 755–761. doi:10.1017/S0266467401001560. ISSN 0266-4674.