Rapid Assessment Survey of the Endangered Silver Bladder Reed Frog (Hyperolius Cystocandicans) in Southern Slopes of Mount Kenya Forest
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Date
2023Author
Karani, Anthony M.
Type
ThesisLanguage
enMetadata
Show full item recordAbstract
Reed frogs are a good case for investigating diversity of reproductive traits associated
with co-occurrence, resource partitioning and habitat heterogeneity. Objectives of this
study were to: (1) establish patterns of co-occurrence and spatial distribution among
frogs in relation with characteristics of habitat patches; (2) identify the distance from
water, spacing between conspecifics and perching height of silver bladder reed frog
(Hyperolius cystocandicans) and other reed frogs, and; (3) estimate the population
sizes and density of reed frogs in the forest on Southern Slopes of Mt. Kenya. Frogs
were searched opportunistically through visual encounter surveys and acoustic
encounter surveys, complemented by use of drift fences and pitfall traps with funnel
traps. Capture mark recapture method was used to generate individual capture history
file that was used to estimate population sizes, capture probability, probability of
entry and probability of apparent survival using POPAN Jolly Seber model in MARK.
Co-occurrence was estimated using pairwise probabilistic model of species cooccurrence
using presence-absence data. The results of this survey showed that H.
cystocandicans co-occurs positively with Amietia nutti, Hyperolius glandicolor,
Hyperolius montanus and Phrynobatrachus kinangopensis and randomly with
Ptychadena mahnerti, Kassina senegalensis, Sclerophrys kerinyagae and Xenopus
borealis. There was interspecific variation in height and spacing of egg masses of H.
cystocandicans and H. montanus but both species deposited their eggs away from
water (terrestrial eggs). Interspecific variation was established in the height of
perching adult reed frogs (H. glandicolor, H. cystocandicans and H. montanus) but
not distance of perching site from water and spacing between conspecifics. The
population sizes of reed frogs per site were: H. glandicolor (123±20.05, 154±99.86,
162±14.85), H. montanus (308±52.12, 50±23.30, 133±10.80; H. cystocandicans
(194±18.24, 101±6.43, 298±38.07). Population estimates were skewed towards males
in H. cystocandicans and H. montanus but not H. glandicolor. With the exception of
H. montanus, the estimated population densities of H. cystocandicans and H.
glandicolor did not vary across survey sites. Population densities did not vary
significantly across species. All species have aquatic larvae but H. glandicolor has
aquatic oviposition site which differs with terrestrial oviposition sites of H. montanus
and H. cystocandicans. It was concluded that this variation drives spatial reproductive
partitioning in distribution of reed frogs in breeding sites which was explained by
interspecific difference in spacing between egg masses, distance of egg masses from
water, height of perching adults and height of egg masses. This study provides
baseline population data that will inform conservation of reed frogs. There is need for
further estimates to determine whether the populations are declining. Future research
should explore genetic diversity in order to estimate the effective population size and
operational sex ratio in male-biased populations.
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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