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Estimating Occurrence and Detectability of a Carnivore Community in Eastern Botswana using Baited Camera Traps

Authors:
  • CONACYT-Guyra Paraguay
  • Mashatu Research, Botswana

Abstract and Figures

Human–wildlife conflict and habitat loss are threatening carnivore populations in southern Africa, where the bulk of research focuses on large predators. However, scant research exists on medium and small carnivore (mesocarnivore) ecology. We employed hierarchical community modelling to estimate the effect of habitat on species occurrence and the effect of bait on detection probabilities for the carnivore community in the Mashatu Game Reserve, Botswana. We tested sites baited with either impala (Aepyceros melampus) meat (meat sites) or cheesecloth soaked in used cooking fat (fat rag sites) against unbaited sites (control sites). Within each bait classification, we divided our sampling effort between two habitat classifications, riverine and non-riverine sites. Thirteen of 16 carnivore species inhabiting the area (81%), including 10 of 12 species of mesocarnivore (83%), were recorded. Occupancy rates were higher in riverine habitat for several species, in particular African civet (Civettictis civetta), brown hyaena (Hyaena brunnea), and large-spotted genet (Genetta tigrina), demonstrating the importance of riverine habitat, which is declining in the study region. Our results suggest that the use of bait improves detectability. Several large carni-vores, including spotted hyaena (Crocuta crocuta), brown hyaena, and leopard (Panthera pardus), were detected at highest rates at meat sites. Many mesocarnivores, including black-backed jackal (Canis mesomelas) and African civet responded equally to meat and fat rag sites, with detections greater than at control sites. Notably, large-spotted genet showed highest detection rates at fat rag sites, and brown hyaena showed higher rates at fat rag sites than control sites. Our detection results indicate that spent cooking fat may be used as an effective bait alternative to meat when studying mesocarnivore communities in southern Africa, whereas meat may still be the most effective for studying large carnivore communities. Identifying effective methods of increasing detection rates will benefit carnivore survey and monitoring initiatives, especially for cryptic species.
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Estimating occurrence and detectability
of a carnivore community in eastern
Botswana using baited camera traps
Lauren C. Satterfield1,2*, Jeffrey J. Thompson3,4, Andrei Snyman5,7,
Luis Candelario1, Brian Rode6& John P. Carroll7
1University of Georgia, Warnell School of Forestry and Natural Resources, 180 E. Green Street, Athens, GA 30602, U.S.A.
2University of Washington, School of Environmental and Forest Sciences, Box 352100, Seattle, WA 98195-2100, U.S.A.
3Guyra Paraguay, Parque Ecológico Asunción Verde, Avda, Carlos Bóveda, Asunción, Paraguay
4National Science and Technology Council (CONACYT) of Paraguay, Justo Prieto 223 esq. Teófilo del Puerto,
Barrio Villa Aurelia, Asunción, Paraguay
5Northern Tuli Predator Project, Mashatu Private Game Reserve, Northern Tuli, P.O. Box 26, Lentswe Le Moriti, Botswana
6BC Field Guide Services (Pty) Ltd., Private Bag X3008, Suite 75, Hoedspruit, 1380 South Africa
7University of Nebraska-Lincoln, School of Natural Resources, 3310 Holdrege St., P.O. Box 830989, Lincoln, NE 68583, U.S.A.
Received 21 June 2016. To authors for revision 2 August 2016. Accepted 3 February 2017
Human–wildlife conflict and habitat loss are threatening carnivore populations in southern
Africa, where the bulk of research focuses on large predators. However, scant research
exists on medium and small carnivore (mesocarnivore) ecology. We employed hierarchical
community modelling to estimate the effect of habitat on species occurrence and the effect
of bait on detection probabilities for the carnivore community in the Mashatu Game Reserve,
Botswana. Wetested sites baited with either impala (
Aepyceros melampus
) meat (meat sites)
or cheesecloth soaked in used cooking fat (fat rag sites) against unbaited sites (control
sites). Within each bait classification, we divided our sampling effort between two habitat
classifications, riverine and non-riverine sites. Thirteen of 16 carnivore species inhabiting
the area (81%), including 10 of 12 species of mesocarnivore (83%), were recorded. Occu-
pancy rates were higher in riverine habitat for several species, in particular African civet
(
Civettictis civetta
), brown hyaena (
Hyaena brunnea
), and large-spotted genet (
Genetta
tigrina
), demonstrating the importance of riverine habitat, which is declining in the study
region. Our results suggest that the use of bait improves detectability. Several large carni-
vores, including spotted hyaena (
Crocuta crocuta
), brown hyaena, and leopard (
Panthera
pardus
), were detected at highest rates at meat sites. Many mesocarnivores, including
black-backed jackal (
Canis mesomelas
) and African civet responded equally to meat and fat
rag sites, with detections greater than at control sites.Notably, large-spotted genet showed
highest detection rates at fat rag sites, and brown hyaena showed higher rates at fat rag sites
than control sites. Our detection results indicate that spent cooking fat may be used as an
effective bait alternative to meat when studying mesocarnivore communities in southern
Africa, whereas meat may still be the most effective for studying large carnivore communi-
ties. Identifying effective methods of increasing detection rates will benefit carnivore survey
and monitoring initiatives, especially for cryptic species.
Key words: Africa, bait, Botswana, camera trap, Carnivora, carnivore, cooking fat, detection,
habitat, Mashatu, meat, occupancy.
INTRODUCTION
With large carnivore populations in decline glob-
ally, continued research on effective conservation
and management strategies is vital for stabilizing
and protecting populations (Ray, Hunter &
Zigouris, 2005; Ripple
et al.
, 2014). These declines
are of particular concern due to the potential role
carnivores play in altering ecosystem dynamics
through trophic interactions (Estes
et al.
, 2011;
Ripple
et al.
, 2014). Consequently, a thorough
understanding of carnivore community ecology is
essential for the conservation of not only carnivore
species, but also the ecosystems that they inhabit.
In southern Africa, extensive research of large
carnivores has a long and enduring history (Caro &
Stoner, 2003; Ogada, Woodroffe, Oguge & Frank,
2003; Ray
et al.
, 2005; Dalerum, Somers, Kunkel
& Cameron, 2008; Snyman, Jackson & Funston,
*To whom correspondence should be addressed.
E-mail: lauren.c.satterfield@gmail.com
African Journal of Wildlife Research 47(1): 32–46 (April 2017)
ISSN 2410-7220 [Print], ISSN 2410-8200 [Online] — DOI: http://dx.doi.org/10.3957/056.047.0032
2015). However, studies on medium and small
carnivores (hereafter mesocarnivores) in the region
are conspicuously lacking given their ecological
importance and the precarious conservation
status of some species (Martinoli
et al.
, 2006).
There is an important need for the development
of efficient, cost-effective, non-invasive sampling
methodologies which adequately survey the major-
ity of species within the carnivore communities of
southern Africa. This need is due to the relative
rarity and cryptic nature of most carnivores, scant
research resources, and often restrictive regula-
tions on data collection in southern Africa’s wildlife
parks and game reserves. Advancement in digital
photography and remote camera (camera trap)
technology meets these needs as it allows for
sampling methods that are minimally invasive, and
low in cost and manpower, while generating high-
quality data (Rowcliffe & Carbone, 2008).
To increase the effectiveness of data collection
using camera trapping, species- or guild-specific
baits are often used to selectively draw carnivore
species to camera trap stations.A literature review
of baits used to lure carnivores yielded the follow-
ing options: peanut butter, eggs, fruit, fish, meat,
offal, blood, live animals, pet food, Calvin Klein
Obsession aftershave, synthetic fatty acid lures,
and carnivore urine (Wilson & Delahay, 2001;
Barea-Azcón, Virgós, Ballesteros-Duperón,
Moleón & Chirosa, 2006; Thorn, Scott, Green,
Bateman & Cameron, 2009; Gil-Sánchez
et al.
,
2011). Many commercial baits, such as carnivore
urine, are difficult to obtain in remote areas of
southern Africa. Others, such as meat, can be
impractical or unsafe to keep in a field camp setting
where refrigeration is scarce. Furthermore, stored
baits have the potential to draw large predators to
field camps and thus into proximity with people.
It is important to consider how baits might influ-
ence behaviour, and thus whether or not bait is
appropriate for the goal of a particular study.
Sampling designs have the potential to signifi-
cantly impact species detectability (Mackenzie &
Royle, 2005; Hamel
et al.
, 2013). Baits have the
potential to alter behaviour through age- or sex-
based divisions in attraction, avoidance, or habitu-
ation, which can further vary by individual and
thus influence heterogeneity of results (Royle,
Magoun, Gardner, Valkenburg & Lowell, 2011;
Foster & Harmsen, 2012). If not accounted for in
study design or analysis, these impacts can skew
interpretation of results. In particular, bait use has
notable potential to influence results of studies
focused demographics due to impacts on species
behaviour (Foster & Harmsen, 2012). However,
studies that rely more heavily on high detection
rates, such as live trapping, population estimation,
or monitoring of cryptic species, can benefit from
bait use (Foster & Harmsen, 2012; du Preez,
Loveridge & Macdonald, 2014). In these cases,
bait can be a valuable tool to improve study design
and save time and resources.
We investigated the importance of riverine habi-
tat to carnivores on the Mashatu Game Reserve,
Botswana. At the time of our study, the remaining
sections of large fever berry (
Croton megalobotrys
)
forest were in narrow strips of 15–100 m along
river banks. Historical photographs of the reserve
show a drastic loss of this riparian habitat over the
last 50 years. While many factors could influence
this habitat change, the leading theory is that this
loss is the direct result of an acute flood amid
sustained drought, combined with increased
elephant (
Loxodonta africana
) populations on the
site (O’Connor, 2010).
These habitat changes are particularly important
in light of increasing human impact on landscapes
throughout southern Africa. These influences
have significant effects on predator communities,
both direct and indirect, which can cascade
throughout trophic levels (Woodroffe, 2000;
Woodroffe, Lindsey, Romañach, Stein & ole
Ranah, 2005; Gusset, Swarner, Mponwane,
Keletile & McNutt, 2009). Therefore it is increas-
ingly important to understand the role of meso-
carnivores in these systems. Reducing stress on
populations, especially through identifying and
protecting vital habitat, can help to mitigate
anthropogenic pressures on car nivores. Regretta-
bly, research investigating the effect of human
activities on the mesocarnivore community is
scarce (Thorn, Green, Dalerum, Bateman & Scott,
2012; Ripple
et al.
, 2014), perhaps due to limited
funds for these less charismatic species and
limited research on effective sampling techniques.
Fortunately, smaller members of the order
Carnivora are gaining some research attention. A
study in the Okavango Delta of Botswana recently
showed that small mammalian species diversity,
and separately carnivore species diversity,
increases in more remote parts of conservation
areas. Results were not reported for small carni-
vores or medium carnivores specifically (Rich,
Miller, Robinson, McNutt & Kelly, 2016). However,
a study on carnivores in Kenya did investigate
species-specific impacts of environmental and
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 33
anthropogenic variables. That study found that
while environmental variables best explain carni-
vore species occupancy, impacts were demon-
strated related to human activities (Schuette,
Wagner, Wagner & Creel, 2013). These general
trends underscore the need for more effective
sampling techniques to support more detailed
mesocarnivore studies.
In addition to assessing the importance of habi-
tats, we evaluated the efficacy of cheesecloth
soaked in used cooking fat against locally harvested
impala (
Aepyceros melampus
) meat in attracting
carnivores on the Mashatu Game Reserve of
eastern Botswana. Meat is a common carnivore
bait but increasingly difficult to obtain in the region
due to hunting restrictions and conflicts with
tourism activities. By contrast, used cooking fat is a
plentiful waste product found in most bush camp
kitchens, making it more accessible and less logis-
tically problematic than meat bait.
To this end, we employed hierarchical community
modelling within a Bayesian framework to estimate
the effect of habitat on occupancy probabilities
and the effect of bait type on detection probabilities
for the carnivore community in the Mashatu Game
Reserve, Botswana. We predicted that habitat
would influence species-specific occupancy rates,
and that riverine habitat would yield higher occu-
pancy rates than non-riverine sites for some
species. This hypothesis is based on years of
presence-only data taken from opportunistic wild-
life surveys conducted by local guides driving and
walking on the property, who observed several
species almost exclusively in riverine areas. We
expected that detection rates for carnivores would
likely be species-specific among baits, and that
detection rates at baited sites generally would be
higher than at unbaited sites. This hypothesis is
due to a presence of both obligate carnivores and
omnivores in the suite of predators studied, and
the predisposition of some species (e.g. brown
hyaenas (
Hyaena brunnea
)) to use scent to find
food, which could increase attraction to bait (Mills,
1987; IUCN, 2013). To our knowledge this was the
first time that used cooking fat was tested as bait
on carnivores in southern Africa, and the first time
that a community occupancy analysis was con-
ducted on the study site.
MATERIALS AND METHODS
Study area
The 3300 ha study area lies in a western land
holding of the 29 000 ha Mashatu Game Reserve
(henceforth ‘Mashatu’) (22°13S, 28°58E), an
unfenced patchwork of private land holdings in
eastern Botswana (Fig. 1a), making it unique in
southern Africa. Mashatu lies within the Northern
Tuli Game Reserve, a 72 000 ha property bordered
on three sides by the Motloutse, Limpopo, and
Shashe rivers. Thus, while connected to vast
expanses of unfenced conservation land, the site
is in close proximity to farms, villages, and other
game reserves.
The region consists of rocky outcrops dispersed
on ancient floodplains along the Motloutse and
Limpopo rivers. Dominant flora on the plains
include mopane (
Colophospermum mopane
),
umbrella thorn (
Acacia tortilis
), and mustard bush
(
Salvadora australis
). Thickets along riverbanks
contain large fever berry trees. According to rainfall
data collected by researchers on the study site
since 1996, average annual total rainfall is approxi-
mately 360 mm, with most precipitation (310 mm
on average) falling during the wet summer months
from November to April and little to no rain (50mm
on average) falling during the region’s dry winter
season from May to October. The study area
supports a suite of 16 carnivore species (Table 2).
Field sampling
We deployed 20 remote infra-red-triggered cam-
eras (Moultrie M80 Game Spy, EBSCO Industries
Inc., Birmingham, AL) housed in locked metal
boxes to prevent theft and damage by animals,
especially elephants, from June to August, 2013
(Table 1).
34 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
Tab le 1. Characteristics of study design and camera sampling effort for a study of carnivore occupancy on Mashatu
Game Reserve in eastern Botswana during June–August 2013.
Dates Bait type
n
Sites
n
Sites 24 h periods Effort
Riverine Non-riverine (days)
12 Jun – 02 Jul Control 415 20 180
03 Jul – 22 Jul Meat 5 5 19 190
12 Jun – 22 Jul Fat Rag 5 5 40 400
1One of the initial 10 cameras failed during the control study and had to be removed from that analysis.It was replaced with a Bushnell
camera (Bushnell Trophy Cam HD, Bushnell Outdoor Products, Overland Park, KS) for the subsequent meat study.
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 35
Fig. 1. Map of southern Africa (inset) and location of the Mashatu Game Reserve study area within the Northern Tuli
Game Reserve, Botswana (a). Location of the Mashatu Game Reserve within the Greater Mapungubwe Transfrontier
Conservation Area (inset) and the location of camera trap sites by bait and habitat classification (b). Research was
conducted during June, July, and August of 2013.
36 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
Tab le 2. Species list within order Carnivora found on Mashatu Game Reserve, Botswana during June–August of 2013. Count of observations at each bait type (CT =
control, MT = meat, FR = fat rag) and, separately, within each habitat classification (RI = riverine, NR = non-riverine) are listed, along with total counts by species. Effort is
given as the cumulative number of sites-days during the study period. International Union for Conservation of Nature and Natural Resources Red List status (LC = Least
Concern, VN = Vulnerable, NT = Near Threatened, EN = Endangered) and IUCN population trend are also listed (IUCN, 2013).
Effort
CT MT FR RI NR TOTAL
(site-days) 180 190 400 375 395 770
Family Species Common name IUCN IUCN Trend
Status
Canidae
Canis mesomelas
Black-backed jackal LC Stable 32 85 199 113 203 316
Otocyon megalotis
Bat-eared fox LC Unknown 2 03145
Felidae
Felis silvestris lybica
African wildcat LC Decreasing 2 2 15 17 2 19
Panthera pardus
Leopard NT Decreasing 8 17 7 22 10 32
Herpestidae
Herpestes sanguineus
Slender mongoose LC Stable 1 11213
Ichneumia albicauda
White-tailed mongoose LC Stable 0 11202
Mungos mungo
Banded mongoose LC Stable 2 34729
Hyaenidae1
Crocuta crocuta
Spotted hyaena LC Decreasing 9 27 17 18 35 53
Hyaena brunnea
Brown hyaena NT Decreasing 3 39 37 63 16 79
Mustelidae
Mellivora capensis
Honey badger LC Decreasing 0 5 8 11 2 13
Viverridae
Civettictis civetta
African civet LC Unknown 3 20 44 67 0 67
Genetta genetta
Small-spotted genet/ LC Stable 0 371910
Common genet
Genetta tigrina
South African large- LC Unknown 1 6 98 101 4 105
spotted genet
1One photograph believed to be
Proteles cristatus
was recorded. However, it could not be verified due to poor resolution, and thus it was excluded from analysis.
Sample sites were unbaited (control sites), or
baited with either impala meat (meat sites) or with
rags soaked with used cooking oil (fat rag sites).
These bait classifications were evaluated by
sampling 10 sites each. Sampling occurred for 40,
20, and 19 days at fat rag, control, and meat sites,
respectively (Table 1). We were most interested in
the effectiveness of fat rags, and chose our design
to allow periods of simultaneous sampling of fat
rags with each of the other two bait types.Thus, fat
rag sites were tested at the same time as control
sites for the first half of the study, and concurrent
with meat sites for the second half of the study,
which lasted 40 days in total.
Sampling sites were placed every ~0.5 km.
Systematic random site placement was used such
that fat rag and control sites were placed alter-
nately (Fig. 1b). Fat rag sites remained in the same
locations throughout the study. After 20 days, con-
trol sites were replaced with meat sites (hung inac-
cessibility within a tree 100 m or less of previous
control sites) and sampling continued for 19 days.
This preserved ~1 km distance between sites of
the same bait classification and at least 0.5 km
between all sites throughout the study.
We were not able to sample all three bait types
simultaneously due to limited camera availability
and logistical constraints in checking camera sites.
Furthermore, our design reduced bias. For exam-
ple, if a meat site was changed to a fat rag site, it
would be difficult to determine if initial visits to the
fat rag bait were due to attraction to the fat rag bait
or memory of the meat bait. Thus, our sampling
design prevented any confounding effects result-
ing from changing a site from one bait type to an-
other.
Placement of sampling sites was stratified by
habitat so that five of the 10 sites within each bait
classification each year were placed in riparian
forest along the Motloutse River (riverine sites),
while the other five were placed away from the r iver
in mopane, mustard bush, and umbrella thorn flats
(non-riverine sites). Thus, an equal number of
sites were sampled for each of two habitat classifi-
cations within each of three bait classifications for
all sampling periods. There was one exception for
control sites, where one camera in a riverine area
was censored due to camera malfunction (Table 1).
From researcher observation, habitat changes
abruptly from riverine to non-riverine habitat. All
riverine sites were at least 1 km away from non-
riverine sites to prevent sampling in any transi-
tional zones.
Because we were investigating a group of carni-
vores with widely varying home range sizes, rather
than an individual species, we do not present an
effective trapping area. Instead, we acknowledge
the confounding effect of indeterminate plot
sizes, as discussed by Efford and Dawson (2012).
Further, we acknowledge the undefined distance
from which an individual could be drawn in to bait
from outside the study area due to acute sense of
smell, making an estimate of maximum site area
particularly problematic for sites at the edge of the
study area. For example, brown hyaenas can smell
scents of even old carcasses from at least 2 km
away (Mills & Hofer 1998). After considering these
factors, combined with the fact that this study was
more concerned with the effects of covariates on
occupancy and detection rather than with spatial
use, we did not attempt to interpret species spatial
use resulting from the occupancy portion of this
analysis. Rather, we focus on covariate effects of
habitat on occupancy probabilities and bait on
detection probabilities.
Fat rags consisted of 30 cm × 30 cm pieces of
cheese cloth soaked in liquid cooking fat (sun-
flower oil, olive oil, butter) left over after cooking
vegetables, eggs, chicken, beef, and pork in the
field camp kitchen. Also, fat was collected and
stored each week after cleaning the kitchen’s fat
trap. The camp has not reported any issues with
carnivores attempting to enter the kitchen to
access food or stored fat.Fat rag sites required two
trees or shrubs located approximately 3–6 m
apart. One plant served as the camera post, while
the other was cut at 0.5 m as a bait post. A single
fat rag was strapped to the top of each bait post
using cable ties. For the bait post, the use of a live
plant was preferred to the use of a stake to hinder
displacement or extraction of the bait post by
elephants.
Meat was obtained from two male impalas
harvested off the property on the first day of the
study. Each impala was field dressed and divided
into five parts consisting of the combined head and
ribcage plus four body quarters. Thus, two impala
yielded all 10 baits needed for each meat site in the
study. Meat was hung on a low, overhanging tree
branch. Branches were selected to make access
by tree-climbing carnivores difficult or impossible.
A 50/50 mixture of water and impala rumen was
poured over the bait. A second tree or shrub,
located 8–10 m away, was used to attach the
camera. By hanging the meat bait in this manner,
we provided a carrion scent lure without risking
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 37
loss of the meat itself. Loss of the bait would
necessitate the harvest of additional impala, an
undesirable scenario given the extreme limits to
acquiring research harvest permits within the
study site. These restrictions were further com-
pounded by the nationwide halt of safari hunting
permits in 2013 as preparation for a blanket ban on
sports hunting across Botswana in 2014 (National
Geographic Society, 2012; Africa Geographic,
2014).
For control sites, a camera was placed on a tree
or shrub and pointed toward an unobstructed
viewing space of at least 8–10 m in diameter.
Cameras were placed along roads or game trails
and baits were refreshed weekly with new fat rags
or by pouring a 50/50 mixture of water and impala
rumen over meat baits. No meat was replaced
during the study period, again due to the difficulty
in securing harvest permits. Cameras were also
checked for functionality and battery life at all sites
during bait refreshment and at least once between
bait refreshments. Cameras operated 24 h/day.
Community occupancy modelling
To estimate site occupancy while accounting for
imperfect detection, we employed a single season
occupancy model within a multi-species hierarchi-
cal Bayesian modelling framework (Dorazio &
Royle, 2005; Dorazio, Royle, Söderström &
Glimskär, 2006). Detection probabilities allow the
model to improve occupancy estimates by predict-
ing how many sites were occupied by the species
in question, even when the species was not
detected. Our modelling approach allowed us to
estimate the effects of habitat classification on
occupancy and baiting method on detectability,
while also permitting estimations for some of the
rarer species through data borrowing that would
not have been possible employing a single species
framework (Dorazio & Royle, 2005). Since the
placement of our sample sites did not ensure that
detections among sites were independent, we
interpret occupancy as site use.
In our model, modified from Dorazio & Royle
(Dorazio & Royle, 2005), we assume that occu-
pancy and detection (R
ij
and
p
ij
respectively) are
each influenced by a species-level random effect
independent of site,
u
i
and n
i
, respectively, and by a
site-level random effect independent of species, "
j
and $
j
respectively (Dorazio & Royle, 2005). We
modelled "
j
and $
j
with linear combination of
parameters representing site-level categorical
covariates for habitat and bait type.
This resulted in the following models:
logit R
ij
=
u
i
+"
j
··
IndR
j
logit
p
ij
=n
i
+$1
i
·
IndM
j
+$2
i
·
IndF
j
where
IndR
j
,
IndM
j
and
IndF
j
are binary indictor
vectors for riverine sites, meat bait sites, and fat
rag bait sites, respectively. Thus, intercept values
represent non-riverine sites for the occupancy
equation and control sites for the detection equa-
tion. We defined a sampling occasion as a 24-hour
period beginning and ending at sunrise each day.
Days that cameras did not collect data (e.g.battery
died, elephants redirected the camera field of
view) were censored in the analysis.
We plotted mean occupancy and detection point
estimates and their 95% Bayesian credibility
intervals that resulted from the model (Figs 2 & 3).
Separately, we reported Bayesian p-values and
95% Bayesian credibility intervals (p-value/BCI)
for the occupancy (Table 3) and detection parameter
estimates (Table 4). Bayesian p-values (hereafter
‘p-values’) serve as an indicator of model fit, with
values near 1 showing strong evidence for the
model covariate and values near 0 showing strong
evidence for the intercept model.For bait covariates,
p-values represented the probability that a bait
had a positive effect on detections as compared to
control sites. For the habitat covariate, p-values
represented the probability that riverine sites
increased occupancy as compared to non-riverine
sites. The significance of this covariate effect was
determined from the mean parameter estimates
and their associated BCIs, where an effect was
considered significant when the credibility interval
did not include zero.
We ran the analysis using WinBUGS (Lunn,
Thomas, Best & Spiegelhalter, 2000) and the
R2WinBugs package (Sturtz, Ligges & Gelman,
2005) for program R v. 3.1.2 (R Core Team, 2014).
We assigned non-informative priors with normal
distributions to parameters and intercepts (Dorazio
& Royle, 2005) using three Markov Chain Monte
Carlo simulation chains with 30 000 iterations, dis-
carding the first 5000 iterations as a burn-in and
thinning chains by 5:1.
All research was conducted under Institutional
Animal Care and Use Committee approval under
Animal Use Protocol number A2013 04-002-Y1-A0
and Botswana Ministry of Environment, Wildlife,
and Tourism Research Permit EWT 8/36/4 XXV
(37).
38 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
RESULTS
Thirteen of the 16 carnivore species known to
inhabit the study area (81%) were detected (Table 2).
African lion (
Panthera leo
), dwarf mongoose
(
Helogale parvula
), and Selous’ mongoose (
Para-
cynictis selousi
) occur on the site but were not
observed during the study. Cheetahs (
Acinonyx
jubatus
) occur at very low densities in the area,
and were thus not included in our list of resident
species (Brassine & Parker, 2015). Wild dogs
(
Lycaon pictus
) have been observed on the site,
but a poaching event in 2012 killed the remaining
mature adults in the area (Andrei Snyman, pers.
obs., June 2013). Thus, we did not consider this
species to be resident as their continued presence
on the site has not been confirmed.
Occupancy results of plotted point estimates
showed that occupancy rates of African civets
(
Civettictis civetta
) and brown hyaenas were higher
at riverine than non-riverine sites (Fig. 2). Parame-
ter estimates (p-value/BCI) gave further informa-
tion about covariate effects.Riverine habitat had a
significant and positive effect on occupancy for
African civet, African wildcat (
Felis silvestris
lybica
), brown hyaena, honey badger (
Mellivora
capensis
), large-spotted genet (
Genetta tigrina
),
and leopard (
Panthera pardus
) (Table 3).
Detection results of point estimates showed
differences in detection rates among bait types for
five species (Fig. 3).Detectability of brown hyaena
was significantly different among all bait types,
with meat sites yielding a higher detection rate
than fat rag sites, and fat rag sites yielding a higher
detection rate than controls. A significant differ-
ence was found for spotted hyaenas (
Crocuta
crocuta
), with meat yielding a higher detection rate
than either fat rag or control sites.Meat and fat rag
sites had similar detection estimates for both
black-backed jackals (
Canis mesomelas
) and Afri-
can civets, which were both significantly higher
than control sites. Also, fat rag sites had signifi-
cantly greater detection point estimates for large-
spotted genets than either unbaited control or
meat baited sites (Fig. 3). Parameter estimates
(p-value/BCI) showed through covariate effects
that meat had a significant and positive effect on
detection for African civet, black-backed jackal,
brown hyaena, honey badger, leopard, and spot-
ted hyaena (Table 4). Fat rags had a significant and
positive effect on detection for African civet, Afri-
can wildcat, black-backed jackal, brown hyaena,
and large-spotted genet (Table 4).
DISCUSSION
Our study represents the first comprehensive
occupancy survey of carnivores in eastern Bot-
swana. These are among the first reported occu-
pancy estimates for many of the species detected
in the Northern Tuli Game Reserve and among the
first to take a quantitative community perspective
on a carnivore complex in southern Africa (e.g.
Schuette
et al.
, 2013; Ramesh, Kalle, Rosenlund &
Downs, 2016; Rich
et al.
, 2016). Our detection of
most of the species found on the study site
suggests that our methods are comprehensive for
surveying and monitoring the carnivore commu-
nity. Our methodology employing baited camera-
trapping methods proved successful in addressing
the issue of the general low detectability of carni-
vores and also demonstrated species-specific
relationships in bait types that will be relevant for
future research. The efficacy of our methodology
in detecting rare and cryptic species is notable in
that we obtained the first recorded evidence of
white-tailed mongoose for our study site, a species
whose occurrence had been suspected, but not
confirmed.
In addition, we found differences in habitat use
among congeneric species. For example, large-
spotted genets had higher occupancy rates at
riverine sites, which are dominated by large
fever berry forest, whereas small-spotted genets
(
Genetta genetta
) exhibited higher use of non-
riverine regions (Table 3). Large-spotted genets
are known to range widely, but prefer wooded
habitats (Fuller, Biknevicius & Kat, 1990), whereas
small-spotted genets will use less wooded habitat if
necessary (Herrero & Cavallini, 2007). To our
knowledge, this is the first study to quantify differ-
ences in habitat use by these sympatric
Genetta
species. Similarly brown hyaena primarily occupied
areas along rivers whereas spotted hyaenas were
recorded mostly at non-riverine sites (Table 3).
Co-occurrence of
Genetta
and hyaena species on
the reserve is possibly a function of niche separa-
tion associated with use of riverine
vs
non-riverine
habitats.
Our lack of detections of African lion, dwarf
mongoose, Selous’ mongoose, cheetah, and wild
dog are likely due to disparate reasons.Wild dogs
were likely extirpated due to a poisoning event just
prior to the start of our research (Andrei Snyman,
pers. obs., June 2013). African lions and cheetahs
are present, but our study area is generally not
within core areas on the reserve for those species.
Additionally, our short sampling period might not
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 39
40 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
Fig. 2. Mean occupancy of carnivore species in the Mashatu Game Reserve, Botswana, during June, July and August of 2013. Mean occupancy estimates and 95%
Bayesian credibility intervals are shown for riverine and non-riverine habitat by species.
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 41
Tab le 3. Estimates for covariate effects of habitat classification on occupancy during 2013 for carnivores on the Mashatu Game Reserve in eastern Botswana. Positive
mean values suggest that the species yielded higher occupancy values in the associated habitat type, while negative values suggest lower occupancy values in the associ-
ated habitat (mean ± 95% Bayesian Credibility Interval). Significant effects (where the BCI does not include 0) are in boldface and italicized. Bayesian p-values assess the
proportion of times out ofn=60000iterations (3 chains × 20 000 iterations) that the parameter on the covariate was greater than that of the control or reference (here
non-riverine habitat is the reference), indicating strength of the habitat effect, with values over 0.5 indicating preference of riverine habitat over non-riverine habitat, and
vice versa
.
Covariate Riverine Non-riverine (intercept values)
Species p-value Mean L_BCI U_BCI p-value Mean L_BCI U_BCI
African civet
1.00 4.97 2.26 8.91
0.00 –3.16 –6.77 –1.02
African wildcat
1.00 6.24 0.86 20.98
0.15 –0.87 –2.70 0.87
Banded mongoose 0.97 6.46 –0.19 21.18 0.50 0.39 –2.18 5.29
Bat-eared fox 0.39 0.13 –3.72 9.77 0.16 –1.04 –3.19 2.08
Black-backed jackal 0.89 4.62 –1.34 19.96
1.00 2.62 0.87 5.89
Brown hyaena
1.00 7.25 1.46 22.01
0.46 –0.05 –1.19 1.14
Honey badger
0.99 6.85 0.98 21.93 0.31 –0.34 –2.41 2.98
Large-spotted genet
1.00 6.69 0.79 21.78 0.17 –0.70 –2.18 0.73
Leopard
0.99 6.73 0.44 22.24 0.79 1.15 –0.81 5.75
Slender mongoose 0.90 5.21 –1.36 20.75 0.48 0.21 –2.93 5.00
Small-spotted genet 0.32 0.04 –6.06 14.34 0.92 1.79 –0.47 6.02
Spotted hyaena 0.12 –1.44 –4.65 0.99
1.00 2.11 0.42 5.05
White-tailed mongoose 0.96 6.09 –0.30 20.76 0.22 –1.43 –6.09 3.15
42 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
Fig. 3. Mean detection of carnivore species in the Mashatu Game Reserve, Botswana, during June, July and August of 2013.Mean detection estimates and 95% Bayesian
credibility intervals are shown for meat and fat rag baits and control sites by species. Note that while detection estimates span from 0 to 1, the
y
-axis is truncated at the high-
est observed detection value.
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 43
Tab le 4. Estimates for covariate effects of bait type on detection based on 20 000 iterations comparing each bait type (fat rag, meat) against unbaited (control) sites for
carnivore baits evaluated on Mashatu Game Reserve, Botswana from June–August 2013. Positive mean values suggest that the bait site yielded greater detection values
than control sites (Mean ± 95% Bayesian Credibility Interval). Significant effects (where the BCI does not include 0) are in boldface and italicized. Bayesian p-values
assess the proportion of times out of n = 60 000 iterations (3 chains × 20 000 iterations) that the parameter on the covariate was greater than that of the control or reference,
indicating strength of the bait effect, with values over 0.5 indicating preference of the bait over the control, and
vice versa
.
Covariate Fat Rag Meat Control (Intercept values)
Species p-value Mean L_BCI U_BCI p-value Mean L_BCI U_BCI p-value Mean L_BCI U_BCI
African civet
1.00 1.85 1.01 2.77 1.00 1.70 0.86 2.66
0.00 –2.84 –3.73 –2.07
African wildcat
1.00 1.58 0.42 2.76
0.85 0.67 –0.75 1.73 0.00 –4.31 –5.42 –3.22
Banded mongoose 0.69 0.33 –1.03 1.65 0.93 0.89 –0.36 1.98 0.00 –4.59 –5.82 –3.46
Bat-eared fox 0.86 0.91 –0.74 2.60 0.85 0.81 –1.14 2.33 0.00 –4.03 –5.87 –2.46
Black-backed jackal
1.00 1.38 0.92 1.84 1.00 1.23 0.74 1.72
0.00 –1.39 –1.81 –0.97
Brown hyaena
1.00 1.24 0.35 2.23 1.00 2.03 1.18 3.05
0.00 –3.14 –4.08 –2.33
Honey badger 0.97 1.17 –0.08 2.45
0.99 1.36 0.27 2.54
0.00 –4.72 –5.93 –3.57
Large-spotted genet
1.00 3.52 2.35 4.62
0.93 0.84 –0.34 1.87 0.00 –3.93 –5.01 –2.79
Leopard 0.23 –0.41 –1.48 0.62
0.98 0.91 0.03 1.73
0.00 –3.17 –3.93 –2.39
Slender mongoose 0.55 0.08 –1.89 1.85 0.90 0.91 –0.64 2.13 0.00 –5.36 –7.03 –3.70
Small-spotted genet 0.96 1.20 –0.16 2.58 0.97 1.22 –0.02 2.40 0.00 –4.93 –6.35 –3.61
Spotted hyaena 0.32 –0.21 –1.06 0.63
1.00 1.36 0.60 2.13
0.00 –2.72 –3.44 –2.02
White-tailed mongoose 0.68 0.44 –1.53 2.29 0.94 1.07 –0.40 2.36 0.00 –5.64 –7.54 –3.80
encompass an entire territorial patrol event for
larger carnivores. These factors, coupled with a
relatively tight camera placement of ~1 km
between similar baits, could render the study area
absent of these species during our sampling
period. Dwarf and Selous’ mongoose are small
and common species that have been observed on
the reserve; however, they are known to have very
small home ranges and are generally considered
to be insectivorous (Creel, 2013). Furthermore,
sites were selected to increase the likelihood to
capturing species along travel routes while consid-
ering the safety of a researcher walking on foot.
Thus, site placement along roads and game trails
may have influenced detection of some species.
Consequently, the spatial scale, site placement,
and baits used in our study might have fundamen-
tally reduced the likelihood of detecting these
species. Finally, limitations in possible survey
days along with small study area size resulted in
low sampling effort for this investigation, as repre-
sented in Table 1, which likely influenced low
detection rates for some species.
Combined information from the detection analy-
sis and parameter estimates give strong evidence
that meat baits are best for members of the large
carnivore guild, in particular leopard and spotted
hyaena, and possibly brown hyaena. While meat
was most effective for brown hyaenas, results
showed that fat rags could also be used effectively
to survey this species.A recent study of baited
ver-
sus
unbaited camera traps in Zimbabwe, where
zebra (
Equus quagga
) meat was used as bait,
supported the need for bait in leopard surveys (du
Preez
et al.
, 2014). Conversely, studies on the
mesocarnivore complex in southern Africa using
fat rags as a lure will likely benefit from similar or
increased species detections with lower costs and
far fewer logistical and permit requirements as
compared to those that employ meat as bait. This
is especially true in the case of large-spotted
genets which showed significantly higher detec-
tion rates at fat rags sites as compared to any other
bait type. Used cooking fat is generated on-site in
camp kitchens and does not present the storage
issues that exist with meat bait.The fat rag method
eliminates the need for harvesting meat on site,
storing meat in camp, or shipping meat from an
external source. Further, it provides a use for a
waste product found in most field camps in south-
ern Africa.
Finally, and perhaps most importantly, fat rags
may also help in studying mesocarnivores in areas
where large predators are common, by specifically
targeting and attracting these subordinate carni-
vores. Use of a universal bait preferred by large
and small carnivores alike, such as impala meat,
when attempting to trap a specific and perhaps
uncommon carnivore species, can logically result
in a situation whereby the target species avoids
the bait site due to the presence of dominant,
inter-specific competitors.
Through employing a systematic sampling
design we were able to quantify the composition
and habitat use of the carnivore community in the
Mashatu Game Reserve in eastern Botswana
while also demonstrating an effective methodology
using baits to address issues of low detectability
typical in carnivore research. Given the inter-
specific difference in habitat use highlighting the
importance of riverine habitats, and given that this
is the first community level study of the carnivore
community in the region, our results serve as an
important reference point for future research,
monitoring, and management of the carnivore
community in eastern Botswana.
To determine if our findings are consistent
across different regions, we suggest that future
research should repeat this study within carnivore
communities similar to the one tested here, and
within communities different to that described
here, in a larger study area employing a higher
sampling effort than our study allowed. Further-
more, future studies should continue to investigate
the effect of fat rag bait on detection by comparing
fat rags to other commonly used bait types such as
eggs or offal in addition to meat. We found that
some species occur at higher occupancy rates in
riverine habitat than in non-riverine habitat. To
determine if finer-scale aspects of habitat (e.g.
vegetation density) also affect occupancy, a
larger-scale study should look at factors influenc-
ing heterogeneity within riverine and non-riverine
habitat areas. Finally, we recommend that future
investigations specifically address the role of habi-
tat in niche separation of sympatric congeneric
species within the order Carnivora to determine if
habitat diversity is integral to the coexistence of
congeneric carnivores.
ACKNOWLEDGEMENTS
We thank the Ministry of Environment, Wildlife
and Tourism and the Department of Wildlife and
National Parks, Botswana, for their cooperation
and permission to conduct our research as well as
Mashatu Game Reserve, in particular Pete le
44 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
Satterfield
et al.
: Estimating occurrence and detectability of a carnivore community in Botswana 45
Roux and David Evans. Additionally, we would like
to thank Anton Lategan and Stuart Quinn for their
continued support of our research and collabora-
tion. We greatly appreciate the advice of Drew
Tyre in finalizing quantitative aspects of the manu-
script. Finally, we thank the University of Georgia
Botswana Field Course students for field assis-
tance. This work was supported by the University
of Georgia Warnell School of Forestry and Natural
Resources, and EcoTraining Inc. We thank these
organizations and individuals for their extensive
financial and logistical support.
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Responsible Editor: F. Dalerum
46 African Journal of Wildlife Research Vol. 47, No. 1, April 2017
... Using impala meat provided by Madikwe from their annual predator management quota, 10 kg portions of bait were set up at half of the camera traps in each cluster to lure predators (Tumenta et al. 2010;Satterfield et al. 2017;Joubert et al. 2020). Trees with single, straight trunks were chosen for bait placement. ...
... Temporal overlap increased with the addition of a baited element at camera trap stations for each pairwise combination, and bait had a significant positive effect on detection probabilities for all three large carnivores. Baited studies have been shown to improve detection rates (du Preez et al. 2014;Satterfield et al. 2017;Joubert et al. 2020) and can aid in increasing capture rates to improve the accuracy of population estimates when targeting elusive species such as leopards (du Preez et al. 2014;Tarugara et al. 2019;Joubert et al. 2020). Furthermore, studies have shown that baits have little to no influence on ranging behaviours (Gerber et al. 2012;du Preez et al. 2014;Braczkowski et al. 2016) and temporal activity (Gerber et al. 2012;Braczkowski et al. 2016) and thus baited studies are still reliable for spatiotemporal analysis of large carnivores (Joubert et al. 2020). ...
Article
Context: The spatio-temporal partitioning of large carnivores is influenced by interspecific competition and coexistence within small, enclosed reserves. Lions (Panthera leo), spotted hyaenas (Crocuta crocuta) and leopards (Panthera pardus) are the three largest African carnivores and have the greatest potential for intra-guild competition, particularly where space is limited. Aim: To investigate the spatio-temporal partitioning between lions, spotted hyaenas and leopards in a small (~75 000 ha), enclosed nature reserve, Madikwe Game Reserve (Madikwe), South Africa. Methods: We deployed 110 camera traps (baited n = 55 and unbaited n = 55) across Madikwe from 26 August 2019 until 6 May 2020. Von Mises kernel density plots were used to investigate daily temporal partitioning among the three species. A multiple-species, single-season occupancy model was used to investigate daily space use patterns. Key results: We found both temporal and spatial exclusion between lions and spotted hyaenas on Madikwe. However, no evidence was found of spatio-temporal partitioning between lions and leopards, and spotted hyaenas and leopards. Conclusions: Exploitative and interference competition on Madikwe might be high enough to warrant spatio-temporal partitioning between lions and spotted hyaenas to avoid the negative effects of intra-guild competition. Contrastingly, patterns observed between leopards and both lions and spotted hyaenas preclude the possibility of top-down control by superior carnivores. Implication: These findings call for an adaptive management approach, where both carnivore and prey species compositions are constantly monitored. Management strategies such as these will allow for the conservation of valuable resources (i.e. prey species) to ensure the persistence of large carnivore populations across African ecosystems.
... However, with this type of study design, it is difficult to separate the effect of lure from other factors that influence detectability, such as species abundance (McCarthy et al. 2013) and local habitat conditions. Furthermore, most studies determine the effect of lure with a single metric-the number of days a species was detected in the presence or absence of lure (Burki et al. 2010, Gerber et al. 2012, Satterfield et al. 2017, Ferreras et al. 2018. Such analyses preclude other ways lure may influence species detectability, such as decreasing time to first detection (i.e., latency to detection; Bischof et al. 2014) or increasing the number of images collected (Rocha et al. 2016). ...
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Motion-triggered camera traps are subject to imperfect detection and thus camera-trapping surveys often try to increase species detectability as part of the study design. One possible way to increase detectability is to use lures, which may encourage a species to investigate a given area. Yet the effectiveness of lures is primarily grounded in anecdotal support. We quantified the effect of a common olfactory carnivore lure on the detectability of mammals near Chicago, Illinois, USA, during 27 August 2018-25 September 2018. We deployed 2 camera traps per site, spaced apart by 100 m, to assess whether lure can modify detectability both within and between sites. At each camera location, we changed lure treatments every 7 days and placed either a lure or a non-lure control in view of each camera following a fully crossed design. For analysis, we developed single-season occupancy models with 3 distinct observational models to quantify whether lure increased the number of days a species was detected, decreased the amount of time to first detection, and increased the number of images collected. Lure induced a subtle change in detectability. Virginia opossum (Didelphis virginiana) responded most to the presence of lure; their daily detection probability rose by roughly 5% and the number of opossum images nearly doubled. However, the effect of lure was often negative for prey species. When lure was present, eastern cottontail (Sylvilagus floridanus) daily detection probability decreased by 5% and they were photographed 63% less often. Likewise, eastern gray squirrel (Sciurus carolinensis) arrived 70% later to a camera trap if lure was present and were photographed 14% less. By using multiple criteria, we were able to better understand how wildlife respond to lure while camera-trapping more thoroughly than would be possible with a single metric. Our results show that lure may not be as effective as expected in terms of increasing detectability, but the choice to use lure should depend on several factors, including the density of the study species, species life history, and the dynamics between the species studied.
... Only a few studies, however, have investigated the effectiveness of attractants for improving the detection of multiple species within a community. Examples of multi-species studies include Paull et al. (2011), studying non-carnivore small mammals in Australia, and studies of carnivores in the Iberian Peninsula, southern Europe and southern Africa (Ferreira-Rodríguez and Pombal 2019;Ferreras et al. 2017Ferreras et al. , 2018Satterfield et al. 2017). ...
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Camera traps are a cost-effective tool for large-scale and long-term population monitoring of mammals. Either bait or lure is often used to attract animals in front of a camera; however, the relative efficiency of these two attractants, or their combination, is not well understood. Our objective was to determine the optimal attractant setup for maximizing detection probabilities of mammals in the northeast USA. We conducted a camera trapping project in northern Maine, USA, from August to November 2018, and tested three distinct attractant treatments against a control. Sampling stations were a minimum of 5 km apart, and consisted of four camera units spaced 100 m apart, and paired with one of the four setups: (1) bait plus lure (treatment), (2) bait (treatment), (3) lure (treatment), and (4) camera only (control). Detection data on 11 species of mammals were collected from 41 stations and analyzed through multi-method occupancy models. We totaled 4280 photo-trap-nights and captured 37,781 images. Results showed that the combination of bait plus lure was the most effective for increasing detection probability of carnivores. Specifically, bait plus lure proved to be particularly effective for mustelid species, while lure was particularly effective for American black bear (Ursus americanus). While attractant usage was shown to be ineffective for increasing detection probability of non-carnivores, it also did not decrease effectiveness. Based on our results, we recommend the simultaneous use of both bait and lure as attractants when conducting camera trapping work on mammals. The combination of bait and lure appears to maximize detection of carnivore species, while simultaneously having minimal effects on the detection of other taxa.
... Statistical modelling and analyses of species' distributions using biological survey data and biotic and abiotic predictors are widely used to understand their distribution. Occupancy modeling represents one approach to estimate carnivores species distribution such as the Saharan cheetah (Acinonyx jubatushecki) in Algeria (Belbachir et al., 2015) and a group of mesocarnivores in the Mashatu Game Reserve, Botswana (Satterfield et al., 2017). This approach controls for heterogeneity in species detectability among sam pling locations based on detection/non detection data and uses maximum likelihood methods to investigate the covariates effect (MacKenzie et al., 2002(MacKenzie et al., , 2006. ...
Article
Differential habitat use and intraguild competition are both thought to be important drivers of carnivore species distributions and abundance. To assess how habitat factors and interspecific interactions affect the structure of this widespread carnivore guild, we developed occupancy models for multi-scale habitat of the following three canids: African golden wolf (Canis lupaster), red fox (Vulpes vulpes) and fennec fox (Vulpes zerda) present in North Africa. Species occurrence records were obtained between January 2014 and January 2016 from 175 sites, covering the southern Tunisia. Occupancies were estimated to be 0.74 ± 0.07, 0.69 ± 0.09, and 0.18 ± 0.06, for red fox, African golden wolf and fennec fox, respectively. Our results showed that distribution constraints for these three canids tend to be linked to human factors, reptile densities and land cover. The co-occurrence models highlighted the interactions between canids. African golden wolf occurrence was unaffected by the presence of other carnivores. Red fox was strongly associated with the African golden wolf. Unlike the African golden wolf, red fox appeared to strongly influence fennec fox occupancy. This study could be valuable for assessing patterns of distribution and impacts of landscape change elsewhere in their ranges.
... ). Much work has been done investigating attractant usage for single species such as brown hyena carnivore small mammals in Australia, and carnivore guilds were studied byFerreras et al. 2017, Ferreras et al. 2018, and Ferreria-Rodriguez et al. 2019 in the Iberian Peninsula and southern Europe, and bySatterfield et al. 2017 in southern Africa. ...
Article
A primary problem with camera trapping in wildlife occupancy studies is the failure to detect an animal when it is present at the site. My objective was to determine the optimal attractant setup for maximizing detection probabilities of northeast mammalian communities. I carried out an camera trapping project in northern Maine, USA from August to November 2018, and tested 3 distinct attractant setup. Sampling stations consisted of four camera units, and each sampling unit constituted either a treatment or a control: 1) bait + lure (treatment), 2) bait only (treatment), 3) lure only (treatment), and 4) camera only (control). Data analysis was conducted in program PRESENCE, using a single season, multi-method occupancy modeling framework. Results showed that the combination attractant of bait + lure was the most effective for maximizing detection probability of carnivores. Bait + lure also proved to be particularly effective for mustelid species, while ‘lure only’ was particularly effective for American black bear (Ursus americanus). Use of attractants was shown to have nearly no effect on detection probability of non-carnivore taxa.
... Although camera traps are a valuable survey method, the use of additional methods in conjunction may also help obtain a more thorough overview of the mammal fauna on these mountains. For instance baiting camera traps could increase trapping rates of mesocarnivores (Moruzzi et al. 2002;Satterfield et al. 2017), whereas the collection and analysis of dung would help identify additional species, particularly herbivores. ...
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The mountains of northern Mozambique have remained poorly studied biologically until recent years with surveys covering a variety of taxonomic groups highlighting their biological and conservation value. Even so, the medium and large mammal fauna remains poorly known and to date no systematic mammal surveys have been published from any of Mozambique’s mountains. We present results of a medium and large mammal survey of Serra Jeci’s Mt Chitagal, Mt Sanga and the Njesi Plateau in Niassa, northern Mozambique; the first mammal diversity data collected from these isolated mountains. We recorded 27 mammal species, of which six represent range expansions; Sykes’s monkey (Cercophitecus mitis), Mozambique dwarf galago (Paragalago granti), Smith’s red rock hare (Pronolagus rupestris), lesser cane rat (Thryonomys gregorianus), rock hyrax (Procavia capensis) and African buffalo (Syncerus caffer). We also reviewed and collated records of medium and large mammals from previously published fieldwork on northern Mozambique’s mountains, amounting to a total of 34 large mammal species from seven montane areas, highlighting the lack of mammalian knowledge in Mozambique’s Afromontane habitats.
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Abstract Counts of independent photo events from camera traps are commonly used to make inference about species occupancy, the density of unmarked populations, and the relative abundance of species across time and space. These applications rest on the untested assumption that data collected from individual cameras are representative of the landscape location in which they are placed, and that nearby cameras would record similar data when any additional micro‐site differences are accounted for. We established a high‐density camera trapping grid (100 × 100 m; 27 cameras) in Virginia, USA, to explicitly test these assumptions, investigating variation in capture rates and detection probabilities for a range of terrestrial mammals during four 2‐month seasonal surveys. Despite controlling for numerous habitat and placement factors, we documented, across all 5 focal species, large ranges and coefficients of variation in both capture rate and detection probabilities, which were similar to those seen across 2 sets of independent forest sampling sites from a larger, more typical camera trap sampling design. We also documented a lack of spatial autocorrelation in capture rate at any distance. Measured local covariates relevant to the camera viewshed (stem density, camera height, log presence, effective detection distance [EDD], total dbh of oak trees) rarely explained any significant portion of observed variation in capture rates or detection probabilities across the grid. The influence of EDD, measured here for the first time for individual camera stations, was inconsistently important and varied in direction of effect depending on species and season. Our study indicates single‐camera stations may fail to sample animal presence and frequency of use in a robust and repeatable way, primarily resulting from the influence of both idiosyncrasies in animal movement and measured and unknown micro‐site characteristics. We recommend spatial replication within sites (e.g., small‐scale shifting of cameras or use of multiple stations) should be considered to minimize impacts of relevant micro‐site characteristics, some of which may be difficult to identify.
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Obtaining reliable species observations is of great importance in animal ecology and wildlife conservation. An increasing number of studies use camera traps (CTs) to study wildlife communities, and an increasing effort is made to make better use and reuse of the large amounts of data that are produced. It is in these circumstances that it becomes paramount to correct for the species-and study-specific variation in imperfect detection within CTs. We reviewed the literature and used our own experience to compile a list of factors that affect CT detection of animals. We did this within a conceptual framework of six distinct scales separating out the influences of (a) animal characteristics, (b) CT specifications, (c) CT setup protocols, and (d) environmental variables. We identified 40 factors that can potentially influence the detection of animals by CTs at these six scales. Many of these factors were related to only a few overarching parameters. Most of the animal characteristics scale with body mass and diet type, and most environmental characteristics differ with season or latitude such that remote sensing products like NDVI could be used as a proxy index to capture this variation. Factors that influence detection at the microsite and camera scales are probably the most important in determining CT detection of animals. The type of study and specific research question will determine which factors should be corrected. Corrections can be done by directly adjusting the CT metric of interest or by using covariates in a statistical framework. Our conceptual framework can be used to design better CT studies and help when analyzing CT data. Furthermore, it provides an overview of which factors should be reported in CT studies to make them repeatable, comparable, and their data reusable. This should greatly improve the possibilities for global scale analyses of (reused) CT data.
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Emerging conservation paradigms have shifted from single to multi-species approaches focused on sustaining biodiversity. Multi-species hierarchical occupancy modelling provides a method for assessing biodiversity while accounting for multiple sources of uncertainty. We analysed camera trapping data with multi-species models using a Bayesian approach to estimate the distributions of a terrestrial mammal community in northern Botswana and evaluate community, group, and species-specific responses to human disturbance and environmental variables. Groupings were based on two life-history traits: body size (small, medium, large and extra-large) and diet (carnivore, omnivore and herbivore). We photographed 44 species of mammals over 6607 trap nights. Camera station-specific estimates of species richness ranged from 8 to 27 unique species, and species had a mean occurrence probability of 0·32 (95% credible interval = 0·21-0·45). At the community level, our model revealed species richness was generally greatest in floodplains and grasslands and with increasing distances into protected wildlife areas. Variation among species' responses was explained in part by our species groupings. The positive influence of protected areas was strongest for extra-large species and herbivores, while medium-sized species actually increased in the non-protected areas. The positive effect of grassland/floodplain cover, alternatively, was strongest for large species and carnivores and weakest for small species and herbivores, suggesting herbivore diversity is promoted by habitat heterogeneity. Synthesis and applications. Our results highlight the importance of protected areas and grasslands in maintaining biodiversity in southern Africa. We demonstrate the utility of hierarchical Bayesian models for assessing community, group and individual species' responses to anthropogenic and environmental variables. This framework can be used to map areas of high conservation value and predict impacts of land-use change. Our approach is particularly applicable to the growing number of camera trap studies world-wide, and we suggest broader application globally will likely result in reduced costs, improved efficiency and increased knowledge of wildlife communities.
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Camera trapping studies have become increasingly popular to produce population estimates of individually recognisable mammals. Yet, monitoring techniques for rare species which occur at extremely low densities are lacking. Additionally, species which have unpredictable movements may make obtaining reliable population estimates challenging due to low detectability. Our study explores the effectiveness of intensive camera trapping for estimating cheetah (Acinonyx jubatus) numbers. Using both a more traditional, systematic grid approach and pre-determined, targeted sites for camera placement, the cheetah population of the Northern Tuli Game Reserve, Botswana was sampled between December 2012 and October 2013. Placement of cameras in a regular grid pattern yielded very few (n = 9) cheetah images and these were insufficient to estimate cheetah density. However, pre-selected cheetah scent-marking posts provided 53 images of seven adult cheetahs (0.61 ± 0.18 cheetahs/100km²). While increasing the length of the camera trapping survey from 90 to 130 days increased the total number of cheetah images obtained (from 53 to 200), no new individuals were recorded and the estimated population density remained stable. Thus, our study demonstrates that targeted camera placement (irrespective of survey duration) is necessary for reliably assessing cheetah densities where populations are naturally very low or dominated by transient individuals. Significantly our approach can easily be applied to other rare predator species.
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The probability that a site has at least one individual of a species (‘occupancy’) has come to be widely used as a state variable for animal population monitoring. The available statistical theory for estimation when detection is imperfect applies particularly to habitat patches or islands, although it is also used for arbitrary plots in continuous habitat. The probability that such a plot is occupied depends on plot size and home-range characteristics (size, shape and dispersion) as well as population density. Plot size is critical to the definition of occupancy as a state variable, but clear advice on plot size is missing from the literature on the design of occupancy studies. We describe models for the effects of varying plot size and home-range size on expected occupancy. Temporal, spatial, and species variation in average home-range size is to be expected, but information on home ranges is difficult to retrieve from species presence/absence data collected in occupancy studies. The effect of variable home-range size is negligible when plots are very large (>100 x area of home range), but large plots pose practical problems. At the other extreme, sampling of ‘point’ plots with cameras or other passive detectors allows the true ‘proportion of area occupied’ to be estimated. However, this measure equally reflects home-range size and density, and is of doubtful value for population monitoring or cross-species comparisons. Plot size is ill-defined and variable in occupancy studies that detect animals at unknown distances, the commonest example being unlimited-radius point counts of song birds. We also find that plot size is ill-defined in recent treatments of ‘‘multi-scale’’ occupancy; the respective scales are better interpreted as temporal (instantaneous and asymptotic) rather than spatial. Occupancy is an inadequate metric for population monitoring when it is confounded with home-range size or detection distance.
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Leopards have the largest natural distribution of felids, but have lost a third of their historical range, and their current CITES status is ‘Near Threatened’. Leopards are a highly sought after trophy species in Africa, although their populations are not monitored in most areas. Zimbabwe sets the highest leopard quota in Africa, but actual offtake does not reflect this, and the number of successful hunts has steadily declined in recent years. Accurate data on leopard populations is urgently needed, particularly where they are harvested. Camera-trapping is a powerful tool for non-invasively researching populations of rare and elusive felids, allowing accurate calculation of population density, and monitoring trends. However, unbaited camera-trapping is plagued by low capture rates, affecting the accuracy of the resultant density calculations. In addition, dependent cubs are underrepresented in the data, precluding an accurate description of demographic structure. We compared baited and unbaited camera-trapping methods and resultant data quality from two survey areas within our study site. Baited camera-trapping significantly increased leopard capture rates, as well as recording dependent cubs, which the unbaited method failed to detect. In addition, the baited method was more cost effective. Using baits to increase capture rates of leopards is more efficient than the unbaited method, and has the potential to accurately survey unmonitored populations; including where their density is too low to determine accurately via other means. These data are required for management of leopard populations, especially where harvested, and may be applied to improve monitoring efforts of other big cat species.
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African lion populations have declined dramatically due to various anthropogenic factors. As a consequence, the majority of extant lion populations are of small size, further compromising their persistence. Lion populations in unfenced areas are more exposed to illegal hunting, snaring and poisoning, while managers of small fenced lions populations often have to limit population growth. Removal of selected individuals in fenced reserves, as opposed to indiscriminate illegal activities, does not necessarily remove the same proportion of individuals from the various age and sex classes. This may therefore affect lion social organization and population demographics differently. From 2000 - 2011, 19 lions from the predominantly unfenced Northern Tuli Game Reserve (NTGR) were shot, snared or poisoned. Just 10km away, only one lioness was shot outside the fenced Venetia Limpopo Nature Reserve (VLNR) where 29 lions were trophy hunted or culled. We found that average population size, sex ratio and litter size were the same for both reserves, but that population density, pride size and cub survival were significantly larger in VLNR. High rates of indiscriminate anthropogenic mortality constrained population size in the NTGR where 94.7% of adult mortality occurred outside the reserve. The two alternate forms of anthropogenic suppression consequently resulted in different population-level responses, ultimately affecting population viability. Lion populations are declining precipitously in Africa, and while current conservation strategies are attempting to remove fences and establish larger conservation areas, this study indicates how fences can influence population dynamics in areas where people threaten large carnivores.
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Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately determine the fate of Earth’s largest carnivores and all that depends upon them, including humans.
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Although carnivores are in global decline, diverse carnivore communities are common in sub-Saharan Africa, where more than 20 species may co-occur. Though intraguild competition and predation can limit the set of species that coexist, most carnivores have traits that decrease the impacts of interspecific competition on fitness, a pattern that promotes coexistence. An increasing human population and demand for natural resources (e.g. farming) has fragmented landscapes, reduced available prey, and elevated rates of conflict. These anthropogenic pressures tend to eliminate large carnivores first, which can have cascading effects on ecosystem function (e.g. mesopredator release). Anthropogenic pressures might also affect mesocarnivores directly, but this hypothesis has received little research attention to date. Here, we used camera surveys to describe spatial and temporal patterns of carnivore occupancy in a mixed-use landscape in Kenya. This landscape included a community conservation area and seasonally occupied human settlement and livestock grazing areas. We detected 21 carnivore species and examined occupancy patterns for the 12 most frequently detected. Differences among species in responses to environmental conditions supported a hypothesis of spatial niche partitioning. Differences in the temporal activity patterns of the apex predators and mesocarnivores supported a hypothesis of temporal niche partitioning. Human land use altered occupancy patterns in 10 of 12 species. Apex predator occupancies were lower in more anthropogenically disturbed areas, but mesocarnivore occupancies were not inversely related to apex predators, contrary to the mesopredator release hypothesis. Our results suggest that a diverse carnivore community persists in this mixed use landscape because of seasonal variation in human land use.
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Hyaena brunnea lives at over twice the density of Crocuta crocuta in the arid S Kalahari, achieved mainly through its more diverse diet, many of the components of which are small and scattered. Spotted hyaena tends to specialise on large and medium-sized mammals. Spotted hyaena territories are 3 times the area of those of brown hyaenas. The social group sizes of the brown hyaena appear to be more responsive to increases in food availability. Both species employ a hinterland method of scent marking rather than border marking. Solitary foraging brown hyaenas also appear to use scent marking to communicate to other group members where they have recently foraged. Spotted hyaenas are the dominant species and may influence brown hyaena numbers where they occur at high densities. -from Author
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This paper reviews field methods for estimating and monitoring the abundance of terrestrial carnivores that do not involve capture. Effective methods of monitoring abundance are important tools for the management and conservation of many species. The development of methods for carnivores presents particular challenges, as they are often secretive and widely dispersed. Nevertheless, a variety of approaches based on direct observations and quantification of field signs have been employed. These techniques are described in relation to carnivore ecology and resource implications, and the advantages and deficiencies of each are discussed with reference to case studies.