Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 July 2022 | 14(7): 21347–21355
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.4943.14.7.21347-21355
#4943 | Received 27 December 2020 | Final
received 10 March 2022 | Finally accepted 01 May 2022
Breeding phenology and population
dynamics of the endangered Forest Spiny
Reed Frog Afrixalus sylvaticus
Schiøtz, 1974 in Shimba
Hills, Kenya
Alfayo Koskei
1, George Eshiamwata 2, Bernard Kirui 3 & Phylus
K. Cheruiyot 4
1 Department of Natural Resources,
Egerton University, Njoro, P.O. Box 536-20115,
Egerton, Kenya.
2 Natural Sciences Programme, Kenya
National Commission for UNESCO, P.O. Box 72107-00200, Nairobi, Kenya.
3 Department of Natural Resources,
Egerton University, Njoro, P.O Box 536-20115,
Egerton, Kenya.
4 Department of Safety, Health and
Environment, Kenya Power & Lighting Company PLC, P.O Box 104 - 20100
Nakuru, Kenya.
1 kkalfayo@gmail.com (corresponding
author), 2 g.eshiamwata@unesco.go.ke, 3 bkkirui@egerton.ac.ke,
4 kphylus@gmail.com
Abstract: Afrixalus sylvaticus Schiøtz,
1974 is a species of hyperoliid frog inhabiting coastal forest Kenya. It is
classified as endangered under IUCN B2ab(iii) ver 3.1
and occurs in the Shimba Hills National Park and
hinterlands. Habitat loss and other human activities are threatening the species.
Therefore, understanding the breeding ecology and population dynamics is
important for its conservation. This study assessed the breeding ecology and
population dynamics of the species in the protected and community landscapes in
Shimba Hills National Reserve in Kenya. Data was
collected through ecological surveys conducted from June 2016 to July 2017
using a visual encounter surveys (VES) method. The results show that the
species was more abundant during the wet season than dry (58% and 42%, respectively).
The population estimate was 192 individuals and a density of 0.98
individuals/km2. Regarding the morphology, the mean snout-vent
length (SVL) for males was 15.12 mm and females 15.96 mm, but there was no
significant difference (t-test = 0.87, p = 0.390, df
= 39). The mean weight of both gravid and non-gravid females was 6.05 g and
males was 4.82 g. The weights were statistically different between both sexes
(t-test = 3.50, p-value = 0.001, df = 39). The sex
ratio was 1:2 (male: female). There was more activity in the wet season (April
and May), and the breeding habitats were reeds and water lilies. The threats
identified to their habitat include; human activities such as bush burning,
livestock grazing, drainage, and plantation of exotic tree species (Eucalyptus
sp.) that have led to habitat loss and degradation. The study recommends that
the reforestation processes such as plantation of exotic species such as Eucalyptus
sp. and Casuarina sp. and bush burning in the wetlands and
species habitats must be discouraged among the stakeholders (community and park
management). Moreover, more synchronized studies are necessary to highlight the
driver(s) of imbalanced sex ratios and species habitat shifts.
Keywords: Amphibians, anura,
ecology, habitat, hyperoliid frog, morphometrics.
Editor: S.R. Ganesh, Chennai Snake Park,
Chennai, India. Date of publication: 26 July 2022
(online & print)
Citation: Koskei,
A., G. Eshiamwata, B. Kirui
& P. K. Cheruiyot (2022). Breeding phenology and population
dynamics of the endangered Forest Spiny Reed Frog Afrixalus
sylvaticus Schiøtz,
1974 in Shimba Hills, Kenya. Journal of Threatened Taxa 14(7): 21347–21355. https://doi.org/10.11609/jott.4943.14.7.21347-21355
Copyright: © Koskei
et al. 2022. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: The project was funded
by International Foundation For Science
(IFS) Project Number: D-5907-1.
Competing interests: The authors
declare no competing interests.
Author details: Mr. Alfayo Koskei (correspondent author) is
tutorial research fellow in the Department of Natural Resources Egerton
University, Njoro, Kenya.Dr.
George W. Eshiamwata is the Deputy Director,
Natural Science Programme, Kenya National Commission
for UNESCO, Dr. Bernard Kirui is a lectturer in
the Department of Natural Resources, Egerton University, Njoro
Kenya and Mr. Phylus
K. Cheruiyot is a Safety, Health and
Environmental Officer, Kenya Power and Lightning Company.
Author contributions: AK—(principal investigator) being
the lead researcher contributed to the data collection, processing and drafting
of the manuscript. GE and BK were project patrons and contributed to data
processing and editing of the manuscript. PKC assisted in field work
coordination, collection of data and proofreading of the manuscript.
Acknowledgements: We appreciate the following
organizations and individuals:
International Foundation for Science (IFS) for funding this project,
Egerton University for provision of research facilities and Kenya Wildlife
Service (KWS) for providing research permits. Shimba
Hills (KWS) Rangers and Management for the special support in field work.
INTRODUCTION
Amphibians throughout the world
are in decline, with 41% of the world’s 6,638 known amphibian species threatened
with extinction (Walls et al. 2017; Grant et al. 2020). A global decline in
amphibians was first recognized in 1989 (Vitt et al.
1998; Wake 1991), and the situation has not improved since then. According to
IUCN (2010a), towards the end of 1998, 124 species of amphibians were
categorized as threatened; but by 2010 the number had increased more than 15
times to 1898 threatened species (Hamer & Parris 2011). This decline
represents 29% of the total number of amphibian species described in the IUCN
Red List (IUCN 2010a), more than any other category of animals. The decline is
likely to have implications on the ecosystem services provided by amphibians
such as biological pest controlling and bioturbation (Valencia-Aguilar et al.
2013).
Afrixalus sylvaticus Schiøtz,
1974 is a species of frog in the family Hyperoliidae (Frost, 2022). The species is categorised
as Vulnerable in the IUCN Red List (IUCN SCC Amphibian Specialist Group 2016),
and the distribution range is limited to Shimba Hills
(Kenya), through the East Usambara foothills in northeastern Tanzania. The species occurs only very
patchily within the mapped range due to limited suitable habitat. Its natural habitats
are dry forests, moist lowland forests, intermittent freshwater marshes, plantations,
and degraded forest.
The primary threat to this
species is habitat loss through drainage of wetlands and afforestation (Bwong et al. 2017). In several areas of prime habitat, the
planting of exotic trees such as Eucalyptus sp. and Casuarina
sp. forests has lowered the water table to such a degree that many
ponds within the coastal dune forest have entirely disappeared (Martin et al.
2004). Along the gradient of Shimba Hills National
Reserve, there are wide-ranging human activities that extend to the protected
area since the reserve policy in Kenya allows human activities within the
national reserves (The Wildlife Act Chapter 376 of 2010). These activities
include resins collection, fuel wood collection, and herbs collection. Shimba Hills is under category “B” together with Arabuko Sokoke Forest Reserve, Ndere Island and Tana Primate Reserve. Along the
gradient of the reserve boundaries, there were human settlement, agro-ecosystems, infrastructure such as roads, making it an
“ecological island.”
Beebee & Griffiths (2005) noted
that the global amphibian decline phenomenon is associated with population
decrease and extinctions in many regions of the world. The need for ecological
studies of amphibians, especially those addressing population dynamics, is a
priority (Houlahan et al. 2000). The main objective
of this research was to assess the breeding ecology and population dynamics of
the species in the protected area and community lands.
MATERIALS
AND METHODS
Study area
We carried out the study in Shimba Hills National Reserve and its hinterlands
(4.2572⁰S, 39.3877⁰E) in Kwale County, Kenya (Figure 1). The area was selected
as it is the only remaining habitat that Afrixalus
sylvaticus is found after the cultivation of rice
schemes in former habitats (Kaloleni areas). The Shimba Hills National Reserve is part of the larger Shimba Hills ecosystem, which also comprises the Mwaluganje Elephant Sanctuary, the Mwaluganje
Forest Reserve, the Mkongani North Forest Reserve and
the Mkongani West Forest Reserve and covers a total
area of 250 km² (Bwong et al. 2017).
Methods
Ecological
surveys were conducted for 60 days in September–December 2016 (dry season) and
another 60 days in April–June 2017 (wet season). The sampling was done along
six transects distributed equally both in protected and unprotected areas. The
unprotected parts were characterized by human activities ranging from agro-ecosystems to settlements and infrastructure. During
the fieldwork , visual encounter surveys (VES) (Crump & Scott 1994: Peek et
al. 2017) were used in all potential microhabitats of the species. The survey
was along the river transect (1,000 m) but
the sampling protocol was adjusted in some areas due to difficult
terrain or at pools of water where line transect was limiting. The number of
individuals encountered within 10m of each side of the transect line was
captured, marked, morphometric/biometric and population attributes recorded.
Marking was by using toe clipping as adopted by (Donnelly et al. 1994).
Morphometric
parameters measured were; snout-vent length (SVL) in mm ±0.01mm, weight (g),
head width (HW), number of resting lines (RL) and population attributes were
sex, age, and other visible traits such as skin colour or visible eggs. The
maturity levels were classifiesd using the presence
of resting lines (that are found usually only in adults). Additionally, we
determined the sex of the individuals using coarseness of the dorsum. Males
have a coarse dorsum, while females have smooth dorsum (Tillack
et al. 2021). Additionally, males develop nuptial pads on the underside of
limbs and toes which facilitate amplexus. These are patches of darkened skin
which are rough to touch. The parameters recorded during sampling include:
seasons, land tenure system, time of the surveys and weather. The population
density within the study areas was determined
using Peterson method (Krebs, 1989) comparing the observed individuals
between sample periods once every month. Chi-square test, ANOVA, and t-tests
were used for comparisons of variables.
Population estimate was determine
using repeat mark-recapture technique
M2C2 M3C3 M3C3
N = ––––– + ––––– + ––––– .................................. (1)
R2 R3 R4
Where:
N-Estimated population size
M-Number Marked in first catch
C-Number caught in second catch
in total
R-Number Recaptured in second
catch
The two sampling periods were
treated as separate marking exercises, as there were no recaptures in wet
period that were marked in dry period. M3 was total of captures in
second month and first month minus the recaptures in second round of sampling
and C3 was total of captures in 3rd month in each
sampling period while R3 was total recaptures in 3rd month.
Population density was estimated using Canonical density estimator since in
some situations, the transect layout was non-uniform (not linear for instance
in water pool).
n
D = ––– ………………………………………………………. (2)
a
Where:
D-Density of the species
N-Total number of animals counted
A-Total area located at
random (transect)
RESULTS
Species occurrences in sampling
sites
Within the protected area, Shimba lodge marshes were densely populated (Wet season: 13
and Dry season: 6). It represents 19% of the entire sampling sites. Other sites
in the protected area were; Manolo and Mwele
catchment (Table 1). In the community lands, Mwandabara
represents the highest population density zone (seven individuals in each
season).
Population size and related
parameters
The total population estimate of
the species was 192 individuals (95% confidence interval) with a density of
0.98 individuals/km2. Generally, the species was more abundant
during the wet season than dry (58% and 42%, respectively). This represents a
significant difference (t-value = -3.38, p-value = 0.002, df
= 30) in the individuals recorded in two different seasons. Land tenure types
in this area are private and public land ownership. The distribution was almost
equal in both land tenure types (51% in protected and 49% in community land).
Regarding the time of the survey, more individuals were encountered during
morning sampling than other sampling periods though there was no significant
difference (F-value = 0.25, df = 2, p-value = 0.781).
Weather played a role in the species capture success as, during the cool and
rainy period we captured the highest number of individuals (47%) as compared to
the cool and dry period (8%) where only five individuals were captured. The
results are shown in Table 2.
Morphology
The mean snout-vent length (SVL)
for males was 15.12 mm, while mean SVL for females was 15.96 mm. The maximum
and minimum SVL of females was 24mm and 4mm respectively, while that of males
was 22 mm and 5 mm, respectively. The SVL for females was higher than that of
males, but there was no significant difference (t-test = 0.87, p = 0.390, df = 39). ANOVA, however, shows that there was a
statistical difference between the mean of males, females, and juveniles SVL
(F-test = 11.00, df = 2, p-value = 0.000).
Consequently, the mean weight of females was higher than males (6.05 g and 4.82
g, respectively). This shows females are significantly heavier than males
(t-test = 3.50, p-value = 0.001, df = 39), a
demonstration that sexual dimorphism is evident in the species. The other
morphometric characteristics taken include head width (HW) and resting lines
(RL). On average, females had higher HW than males (4.3 mm and 3.5 mm). The
resting lines were more related to both males and females but were missing in
juveniles. On average both male and female had 1.59 and 1.2 resting lines
respectively whereas juveniles had none (Table 3).
Population structure and sex
ratio
There were more individuals
captured during the wet period (57.4%) as compared to the dry period (42.3%).
In terms of population structure, the largest proportion are females (29) and
juveniles the smallest (10). There was no significant difference across all
categories (Pearson chi-square = 2.068, df = 2,
p-value = 0.356). Sexual dimorphism in young individuals was difficult to point
out, and we classified them as juveniles (Table 4).
The sex ratio was relatively
stable throughout the sampling period, but females were more than male, an
indicator of the population’s reproductive potential (Yildiz
& Göcmen 2012). The sex ratio was 1:1 in the year
2016, but the following year it was 1:2 in favor of
females.
Activity period and breeding
ecology
Activity periods
The activity of the amphibians is
associated with calls. We recorded a number of calls of the species and other
species in each habitat for five hours every sampling period, a reflection of
the activity period (Table 6). The mean calls show there was more activity in
the wet than the dry season. On maximum, four calls/min were recorded in dry at
2000 h. This was the time with maximum activity (x = 0.875calls/min) as
the number of calls peaked (Figure 2). In wet season, however, the maximum
activity period was at 1900 h. In both periods, the number of calls declined
from 2000 h and was lowest at 2200 h.
In comparison with other species
in each habitat, the A. sylvaticus calls
represents a small proportion. There average calls of other species combined
were above 4.5 calls, and the maximum was 7.7 calls/min (Figure 3). Like the A. sylvaticus,
the mean number of calls of other species also declined after 2000 h and was at
lowest as 2200 h.
Breeding
ecology
During the
activity periods, some solitary and mating pairs of A. sylvaticus
were seen in the reeds and water lilies in waterlogged habitats (Image 1a,b).
We captured one pregnant female notable from a swollen abdomen. After two days,
we found the spawn deposited at the place (Image 2a). In some situations, spawn
were also deposited in leaf foldings. The breeding of
the species was predominantly on reeds and water lilies (Image 1a,b and 2b).
The breeding period was confined to the months of April and May, during which
the highest number of calls were recorded (Figure 4).
Influence
of human activities on species population attributes
Although
wetlands such as marshes and water pools were abundant in human occupied lands
including Mwandabara and Kivumoni,
human activities such as bush burning, livestock grazing, drainage, and
plantation of exotic tree species (Eucalyptus sp.) has converted most
wetlands to terrestrial habitats and limit the species occupancy. However,
there was no significant difference in species population between protected
area and community area (At 95% CI, P-Value = 0.795, DF = 36).
DISCUSSION
Population
Size, Structure and Dynamics
The
abundance of the species during the wet season demonstrated the synchrony of
breeding with season and availability of breeding habitats such as water pools
and moist reeds. The species deposit the spawn masses in the aquatic plants.
While there was no previous study outlining the population status of the
species, the IUCN Red List indicates the species is declining. In the study
sites, numerous human activities such as wetland drainage, livestock grazing in
wetlands and bush burning are attributed to the decline of the species
population. Habitat loss has received much attention as a driving factor in
amphibian declines and is widely considered one of the leading causes (Gallant
et al. 2007; Gardner et al. 2007).
During dry
weather, most sightings were largely of adults, as compared to the wet season,
when there were more sightings of juveniles. This difference can be attributed
to the influence of temperatures and favorable
breeding weather. Temperature and moisture influence amphibian ecology,
physiology, and behavior because amphibians must
maintain moist skin for oxygen and ionic exchange and temperature influences
metabolic rates (Burrowes et al. 2004; Blaustein et al. 2010). Additionally, apart from
particulate dynamics, tadpoles may be influenced by dissolved nutrients in
streams (Hamer & Parris 2011), especially in the dry season when densities
are high and flow is relatively low.
The species
is not very mobile as it is endemic to Shimba Hills (Spawls et al. 2019) and we hold the assumption that the
marking did not affect their movement or catchability. The population size and
density of this species are insignificant compared to other amphibians in the
area (192 individuals and density of 0.98/km2). Many factors are
significant in influencing the small species population. In the previous field
surveys, the species was sighted in Kivumoni Gate
Swamp, Marere headworks, Sheldrick
Falls, and Shimba Lodge Swamp (Bwong
et al. 2017). However, we made a transect sampling in some of these sites, but
there was no capture for the entire survey (both in the dry and wet season).
This suggest a potential shift in species habitat or decline in the species
population. Stuart et al. (2004) projected that the loss of habitat is relevant
to all regions and is also linked to habitat fragmentation and degradation.
In other
studies, conducted elsewhere, Hamer & Parris (2011) noted that in tropical
regions, the roles of amphibians in both aquatic and terrestrial habitats are
more consistent through time because of their more stable seasonal abundance
patterns, high species richness, and diversity of reproductive modes. In this
species, however, there was an unstable age structure, more females, few
juveniles, and few males.
Schmidt et
al. (2002) noted that the estimation of basic demographic parameters and the
identification of their determinants are essential to improve the understanding
of population dynamics and life histories of amphibians. The general
observation from the survey shows declining habitats, as some wetlands are
converted to farmlands, livestock grazing fields, and tree plantations (Image
1a and b).
Morphology
Afrixalus is a sub-Saharan genus containing about 35
taxa (Pickersgill 2005). Most of the members in this
genius are referred to as ‘dwarf’ because of their small body length and
weight. The term ‘dwarf’ was loosely applied to species which did not exceed 25
mm in length (Pickersgill 2005). This species
averaged less than 24 mm in SVL and weighs about 6.05 g.
In A. sylvaticus recorded in Tanzania, the males’ length was
between 15.2–21.1 mm (mean 18.1 mm, N = 28), females 17.2–25.0 mm (mean 20.3
mm, N = 41) (Pickersgill 2005). This morphometrics
features confirms the relationships of the species in different habitats and
the sexual dimorphism where female is slightly larger in size than males. It
was also evident that males are fewer than females, but the reason for the
variation is still not clear. Schiøtz (1999) records
a snout-vent length of up to 24 mm in females with dorsal asperities fine and
weak, confined to head or at least not extending to tibiae and feet; gular disc
with or without fine asperities; no ventral asperities. Additionally, Schiøtz recorded the length of males from 18.0–20.8 mm
(mean 19.4 mm, N = 17), females 20.6–22.8 mm (mean 21.8 mm, N = 3).
In most
anurans, females are bigger than males, but males are bigger in some species in
which males have physical competition for mating (Shine 1979). The principal
diagnostic characters in Afrixalus are mostly
secondary sexual characters present only in male frogs (Pickersgill
1984). For this reason, outside the species descriptions, all morphological
analyses of frogs are based on sexually mature males. Afrixalus
are often known as Spiny Reed Frogs due to the presence of minute spinules, or asperities, in the skin of most species. We
followed the detection technique previously used (Pickersgill
1984). The primary means of detection was through a 10X or 20X hand lens, with
the wet specimen held at an angle to a light source so that as the fluid
evaporated from the skin, the asperities pierced the surface film. In most
mature individuals we captured, the color of the
dorsum was silverish to greenish-yellow, usually with
scattered dark spots and with up to three darker transversely oriented bands
which we labeled resting lines.
Breeding
ecology and activity periods
According
to Pickersgill (2005), this species is commonly
referred to as ‘Leaf folding Frogs’ because of the typical mode of oviposition,
they occupy a range of habitats from seasonally moist open grassland and
savanna to rain forest, and from sea level to altitudes above 2,000 m. Though
it was not found in savanna, there was evidence that it occupies the moist
grassland during the dry period, as was the case in Mwandabara
and Marere. However, the species is commonly found in
reeds and wetland vegetation in water lilies and reeds.
Forest
species produce some of the shortest and simplest Afrixalus
calls, and voice evolution in the closely related species A. stuhlmanni complex, may reflect a transition between
forest and savanna habitation (Pickersgill 2005). An
analysis of voices in the genus Afrixalus
shows a gradual increase in the number of pulses per call, from A. sylvaticus with 2–5 pulses to the dry savanna (Martin
et al. 2004; Pickersgill 2005). While we also noted
the variation in habitats, we did not compare the wetlands to savanna. It was
only evident that the calls vary significantly between the dry and wet season.
This is attributed to the activity of breeding influenced by a rainy period. Pickersgill (2005) also found the variation in the number
of calls in different temperature conditions and concluded that there is a
negative correlation between number of calls and temperature.
We found
more activity during the wet period than dry, and consequently, more captures
were done during the cold and rainy weather. The activity was high in the month
of April, with heavy rains, but it declined in the subsequent months of May and
June (2017). This confirms the breeding period peaks in wet season and not
common in the dry season.
Conclusion
The
distribution of the species is patchy and limited to some regions within the
study area. There was evidence that the species is shifting sites or declining
in their numbers as some of the previous sites no longer support the species.
Some sites are shrinking in size and habitat quality, such as Kivumoni and Mwandabara. There is
an imbalance in sex ratio, and more synchronized population dynamic studies are
needed to highlight the driver(s) behind the male decline. Moreover, efforts to
safeguard the species habitats, especially in community lands, are essential to
enhance the species niches.
Table 1. Number of Afrixalus sylvaticus
captured in each transect during wet and dry seasons.
|
Dry season |
(%) |
Wet season |
(%) |
Total |
Kivumoni |
4 |
44 |
5 |
56 |
9 |
Marere |
2 |
50 |
2 |
50 |
4 |
Mwandabara |
7 |
50 |
7 |
50 |
14 |
Manolo |
3 |
38 |
5 |
63 |
8 |
Mwele catchment |
3 |
60 |
2 |
40 |
5 |
Shimba lodge |
6 |
32 |
13 |
68 |
19 |
Total |
25 |
42 |
34 |
58 |
59 |
Table 2. Population size and
related parameters.
Parameter |
Category |
N |
Mean |
SE (±) |
SD (±) |
Min |
Max |
Percent |
Season |
Dry |
25 |
1.042 |
0.0417 |
0.204 |
1 |
2 |
42 |
Wet |
34 |
1.417 |
0.103 |
0.504 |
1 |
2 |
58 |
|
Land tenure type |
Protected area |
30 |
1.364 |
0.064 |
0.326 |
1 |
2 |
51 |
Community area |
29 |
1.115 |
0.105 |
0.492 |
1 |
2 |
49 |
|
Time of survey |
Evening |
18 |
1.286 |
0.125 |
0.469 |
1 |
2 |
31 |
Morning |
21 |
1.235 |
0.106 |
0.437 |
1 |
2 |
36 |
|
Night |
20 |
1.177 |
0.095 |
0.393 |
1 |
2 |
34 |
|
Weather |
Cool and dry |
5 |
1.667 |
0.333 |
0.577 |
1 |
2 |
8 |
Cool and rainy |
28 |
1.167 |
0.078 |
0.381 |
1 |
2 |
47 |
|
Hot and dry |
8 |
1.000 |
0.000 |
0.000 |
1 |
1 |
14 |
|
Warm and dry |
18 |
1.385 |
0.140 |
0.506 |
1 |
2 |
31 |
Table 3. Morphometric
characteristics of Afrixalus sylvaticus.
Parameter |
Sex |
Mean |
SE |
SD |
Var |
Min |
Max |
SVL(mm) |
Female |
15.96 |
1.22 |
5.73 |
32.86 |
4 |
24 |
Juvenile |
5 |
1.98 |
5.23 |
27.33 |
0 |
13 |
|
Male |
15.12 |
1.11 |
4.83 |
23.37 |
5 |
22 |
|
Wg(g) |
Female |
6.05 |
0.228 |
1.069 |
1.143 |
3.4 |
7.2 |
Juvenile |
0.9429 |
0.0481 |
0.1272 |
0.0162 |
0.8 |
1.1 |
|
Male |
4.821 |
0.229 |
0.996 |
0.993 |
2.9 |
6 |
|
Hw(mm) |
Female |
4.318 |
0.363 |
1.701 |
2.894 |
3 |
5 |
Juvenile |
1.143 |
0.634 |
1.676 |
2.81 |
0.2 |
2 |
|
Male |
3.579 |
0.377 |
1.644 |
2.702 |
1.2 |
4 |
|
RL(Count) |
Female |
1.591 |
0.17 |
0.796 |
0.634 |
0 |
3 |
Juvenile |
0 |
0 |
0 |
0 |
0 |
0 |
|
Male |
1.211 |
0.164 |
0.713 |
0.509 |
0 |
3 |
Table 4. Population structure.
|
Dry season |
(%) |
Wet season |
(%) |
Total |
Female |
10 |
34.48 |
19 |
65.52 |
29 |
Juvenile |
4 |
40 |
6 |
60 |
10 |
Male |
9 |
45 |
11 |
55 |
20 |
Total |
25 |
42.37 |
34 |
57.63 |
59 |
Table 5. Sex Ratio
Year |
Sampling 1 |
Sampling 2 |
Sampling 3 |
Annual |
2016 |
1:2 |
1.3:1 |
2:1 |
1:1 |
2017 |
1:1 |
4:1 |
1.3:1 |
2:1 |
Table 6. Activity periods
Variable |
Season |
Mean |
SE |
SD |
Var |
Min |
Max |
1800 h |
Dry |
0.625 |
0.189 |
0.924 |
0.853 |
0.000 |
3.000 |
|
Wet |
0.750 |
0.150 |
0.737 |
0.543 |
0.000 |
2.000 |
1900 h |
Dry |
0.500 |
0.147 |
0.722 |
0.522 |
0.000 |
2.000 |
|
Wet |
0.875 |
0.193 |
0.947 |
0.897 |
0.000 |
3.000 |
2000 |
Dry |
0.875 |
0.220 |
1.076 |
1.158 |
0.000 |
4.000 |
|
Wet |
0.708 |
0.175 |
0.859 |
0.737 |
0.000 |
3.000 |
2100 h |
Dry |
0.583 |
0.190 |
0.929 |
0.862 |
0.000 |
3.000 |
|
Wet |
0.667 |
0.155 |
0.761 |
0.580 |
0.000 |
2.000 |
2200 h |
Dry |
0.375 |
0.132 |
0.647 |
0.418 |
0.000 |
2.000 |
|
Wet |
0.625 |
0.145 |
0.711 |
0.505 |
0.000 |
2.000 |
The figures in bold represent the highest and
lowest mean number of calls.
For
figures & images - - click here (for full PDF)
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