Assemblage Composition and Feeding Ecology of Sympatric Lacertilians in Kenting Area

  • 謝 章壬

Student thesis: Master's Thesis


Suborder Lacertilia of order Squanmata is comprised of lizards and geckos that are prevailing around the world Different habitat types are comprised of specific environments and resources thus result in different assemblage compositions The study investigated (1) the effects of environmental factors on lizard assemblage compositions and distribution patterns among different habitat types (2) habitat selection of different species in each habitat type (3) the diet compositions with different foraging strategies of lizards and (4) how the prey types and the interactions among species affect the foraging behaviors of geckos Lizards are ectotherms so that temperature-related factors including ambient temperature wind speed relative humidity and the amount of solar radiation may influence their activity patterns directly or indirectly I tested the hypothesis that closely-related sympatric taxa often reveal resource partitioning which may influence assemblage compositions The study site was situated in the Guililaou Exprtimental Forests Kenting area I set 198 grids which were 20 m × 20 m in size in four habitat types including plantations fragmented woods of forest edge intact woods with continuous canopy and grasslands I conducted 4-5 day field works twice a month from January 2012 to May 2013 When surveyed in grids I used visual encounter method and recorded the lizards in 10 minutes The grids were further classified into three vertical levels where the tree canopy coverage shrub crown coverage and the proportion of each ground coverage were estimated I recorded 8 species of lizards and 4 species of geckoes They included Swinhoe’s japaluras (Japalura swinhonis G?nter 1864 Agamidae) Sauter’s grass lizards (Takydromus sauteri Van Denburgh 1909 Lacertidae) elegant skinks (Plestiodon elegans Boulenger 1887) long tailed skinks (Eutropis longicaudata Hallowell 1856) common sun skinks (Eutropis multifasciata Kuhl 1820) formosan smooth skinks (Scincella formosensisVan Denburgh 1912) brown forest skinks (Sphenomorphus incognitus Thompson 1912) and Indian forest skinks (Sphenomorphus indicus Gray 1853) of the family Scincidae and common house geckos (Hemidactylus frenatus Schlegel 1836) Bowring’s geckos (Hemidactylus bowringii Gray 1845) Hekou’s geckos (Gekko hokouensis Pope 1928) and common smooth-scaled geckos (Lepidodactylus lugubris Dum?ril and Bibron 1836) of the family Gekkonidae The mean abundance and richness of diurnal lizards were higher in both plantations and fragmented woods of forest edge while geckos revealed no differences among these habitat types at night The heterogeneity of lizard assemblages was the highest in plantations whereas evenness peaked in fragmented woods of forest edge at daytime and plantations at night respectively Sphenomorphus incognitus dominated plantations but J swinhonis was the most abundant in other three habitat types Among geckos G hokouensis was the prevailing species in all habitat types whereas H frenatus occurred in grasslands most frequently Temperature was the essential factor that influenced the distributions of the three most dominant lizards J swinhonis E longicaudata and S incognitus Japalura swinhonis preferred the habitat with higher tree density on the other hand E longicaudata and S incognitus exhibited no habitat preferences and avoided shrub and exposed land I totally captured four species Both S incognitus and S indicus contained comprised four orders of arthropods in the fecal samples The diet of both J swinhonis and E longicaudata comprised of 10 same orders of arthropods along with some lizard remains In addition J swinhonis were found ingesting plant items and E longicaudata consuming snails Coleoptera Hymenoptera and Orthoptera accounted for 66% relative frequency and more than 75% volume of the diet composition of J swinhonis In the diet of family Scincidae Hymenopterans and Orthopterans were the main food items accounting to 38% of relative frequency and more than 50% of volume The difference of morphology and foraging strategy between lizards cause the difference on the diet compositions The study used three sympatric geckos H frenatus H bowringii and G hokouensis to investigate the differences in foraging behaviors when capturing the same or different prey I chose eight buildings in the Hengchun Tropical Botanical Garden (HTBG) to observe the behaviors of geckos I recorded the foraging behaviors of geckos at night from June 2012 to September 2013 I tested the hypothesis that prey type and prey size will influence gecko foraging performances I also tested the hypothesis that the foraging behaviors of geckos will be affected by species number and distance to neighboring geckos The activity time of most geckos initiated from 19:00 to 04:00; however the movement pattern of each species was different The abundance of H frenatus reached to the peak at about 19:00 but the abundance of H bowringii and G hokouensis were similar of each hour all night The feeding rate feeding success rate and feeding efficiency were similar among these gecko species When these three geckos captured lepidopterans they showed similar foraging behaviors Hemidactylus frenatus predated five insect orders and one gecko species Once capturing geckos the approaching latency was higher than capturing insects while the approaching distance was the shortest in capturing dipterans Hemidactylus bowringii hunted lepidopterans with a faster approaching speed than hunting Hymenopterans whereas G hokouensis showed similar foraging behaviors when capturing coleopterans and lepidopterans The approaching latency speed and distance of H frenatus all increased with increasing prey size; although only the approaching distance of H bowringii and the approaching latency of G hokouensis will increase with increasing prey size The kind of species of the nearest gecko and the distance between two foraging geckos did not affect the foraging behaviors of each species The mean approaching speed of H frenatus decreased with the increasing number of neighboring geckos The number of nearby individuals did not affect the feeding rate of these three geckos but the success rate of H frenatus decreased with the increasing number of neighboring individuals The results indicated that lizards had more opportunities to do their thermoregulation in the plantations which revealed the highest species richness and abundance Moreover when encountering different prey the prey species and size affected the foraging behaviors The number of nearby individuals will cause differences patterns in foraging behaviors which influence the subsequent feeding success rate Even H frenatus had higher aggressive characteristics with more advantage to resource competition than other two species the foraging behaviors of H frenatus still affected by other gecko species Therefore the feeding success rate of H frenatus decreased
Date of Award2014 Sep 10
Original languageEnglish
SupervisorYa-Fu Lee (Supervisor)

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