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\begin{document}

\title{Super-scavengers: Vertebrates outperform invertebrates and microbes at
removing carrion from a tropical forest}



\author[1]{Bhavya Iyer}%
\author[1]{Sutirtha Dutta}%
\author[1]{Qamar Qureshi}%
\author[1]{Yadvendradev Jhala}%
\affil[1]{Wildlife Institute of India}%


\vspace{-1em}



  
  \date{May 24, 2024}


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\selectlanguage{english}
\begin{abstract}
Scavenging by vertebrates is an important ecosystem service as they are
known to remove carrion more efficiently than other taxa. How long would
carrion persist bereft of vertebrate scavengers? Our study addresses
this question in a forested landscape, by comparing carrion utilization
by vertebrate scavengers, invertebrates, and microbes (decomposers). To
understand carrion removal, we used experimental placement of chicken
carcasses in a dry deciduous forest near Panna Tiger Reserve, Madhya
Pradesh, India. Carcasses were placed under different treatment
conditions (vertebrate scavenging, invertebrate scavenging, microbial
decomposition and control to account for moisture loss), by
experimentally excluding other scavengers. The daily rate of carcass
utilization and proportion of carrion biomass remaining differed between
treatments. Vertebrates consumed carcasses at the highest rates,
removing 83\% of carcass biomass in one day (CI 95\%), followed by
invertebrates (7.3\%) and microbes (3.9\%). Additionally, desiccation
accounted for another 3.6\% weight loss per day. The study showed
drastic differences in carrion removal rates between taxa, indicating
the irreplaceable role of vertebrates in the scavenging community of
tropical forests, without whom carcasses would persist over prolonged
periods. Our results support earlier studies that found overwhelming
influence of vertebrate scavengers on carrion removal compared to other
scavenging guilds.%
\end{abstract}%



\sloppy


Super-scavengers: Vertebrates outperform invertebrates and microbes at
removing carrion from a tropical forest

Authors

Bhavya Iyer, Sutirtha Dutta, Qamar Qureshi, Yadvendradev V. Jhala

Wildlife Institute of India, Chandrabani, Dehradun, 248001, India.

Correspondence

Bhavya Iyer

Wildlife Institute of India, Chandrabani, Dehradun, 248001, India.

Email: bhavyaiyer94@gmail.com

Abstract

Scavenging by vertebrates is an important ecosystem service as they are
known to remove carrion more efficiently than other taxa. How long would
carrion persist bereft of vertebrate scavengers? Our study addresses
this question in a forested landscape, by comparing carrion utilization
by vertebrate scavengers, invertebrates, and microbes (decomposers). To
understand carrion removal, we used experimental placement of chicken
carcasses in a dry deciduous forest near Panna Tiger Reserve, Madhya
Pradesh, India. Carcasses were placed under different treatment
conditions (vertebrate scavenging, invertebrate scavenging, microbial
decomposition and control to account for moisture loss), by
experimentally excluding other scavengers. The daily rate of carcass
utilization and proportion of carrion biomass remaining differed between
treatments. Vertebrates consumed carcasses at the highest rates,
removing 83\% of carcass biomass in one day (CI 95\%), followed by
invertebrates (7.3\%) and microbes (3.9\%). Additionally, desiccation
accounted for another 3.6\% weight loss per day. The study showed
drastic differences in carrion removal rates between taxa, indicating
the irreplaceable role of vertebrates in the scavenging community of
tropical forests, without whom carcasses would persist over prolonged
periods. Our results support earlier studies that found overwhelming
influence of vertebrate scavengers on carrion removal compared to other
scavenging guilds.

Keywords

Carcass, mesopredators, vultures, central India, Panna, decomposers

\section*{Introduction}

{\label{introduction}}

Vertebrate scavengers consume an estimated 75\% of carrion around the
world (Devault \emph{et al.} , 2003). Yet, scavenging by vertebrates, as
a process had gained recognition only recently. Vertebrate scavengers
play important ecosystem functions such as nutrient cycling
(Cederholm\emph{et al.} , 1999; Danell, Berteaux and Br\selectlanguage{ngerman}åthen, 2002)
sanitation and disease moderation (Markandya \emph{et al.} , 2008), and
competitive interactions (Kaczensky, Hayes and Promberger, 2005;
Materassi \emph{et al.} , 2017). Scavenging retains nutrients from
carrion and recycles them in the biotic component of the ecosystem that
would otherwise get released into the physical environment through
decomposition, thereby playing a regulatory role in biogeochemical
cycles (Danell, Berteaux and Bråthen, 2002). Instead of allowing
carcasses to decompose completely at a site, leading to a large `island'
of nutrients which may persist over years (Danell, Berteaux and Bråthen,
2002; Benninger, Carter and Forbes, 2008; Parmenter and Macmahon, 2009)
vertebrate scavengers, in particular, assist in dispersing these
nutrients over a larger landscape. This reduces the excessive
concentration of nutrients such as Phosphorus, Sodium and Potassium
around carrion (Benninger, Carter and Forbes, 2008; Parmenter and
Macmahon, 2009) which would inhibit vegetation growth (Towne, 2000).
Obligate vertebrate scavengers remove carrion more efficiently and
rapidly than facultative scavengers or decomposers (Ogada \emph{et al.}
, 2012). The highly acidic digestive tract and gut microbiome of
specialized scavengers such as vultures reduces the transmission of
pathogens and consequently the risk of disease spread from decomposing
carcass (Houston and Cooper, 1975; Roggenbuck \emph{et al.} , 2014;
Graves, 2017; Zepeda Mendoza \emph{et al.} , 2018). In the absence of
obligate vertebrate scavengers, accumulation of carrion over longer
durations, competitive release of facultative scavengers, and disease
transmission through facultative scavengers can have serious ecological
ramifications that are poorly understood. In light of the global
declines of vertebrate populations, understanding these aspects of
carrion ecology becomes vital. Such insights can bolster the scientific
rationale and global efforts for conservation of vertebrate populations.

Quantifying the relative contribution of vertebrate scavengers to
carrion removal in comparison with invertebrate scavengers and microbial
decomposition allows us to better understand the role of different
scavenging communities, which in turn can inform conservation policy.
Conserving the diversity of scavenger assemblages is important in the
light of biodiversity loss (Cardinale \emph{et al.} , 2012), as this
enhances functional redundancy, thereby stabilizing scavenging systems.

Previous studies have shown that manipulative reduction of a dominant
scavenger (raccoons \emph{Procyon lotor} ) in an agricultural landscape
reduced system efficiency and left more carcasses un-scavenged
(Olson\emph{et al.} , 2012). Exclusion of vultures from carcasses did
not increase carcass visitation or utilization by facultative scavengers
and resulted in 10-fold greater un-scavenged carcasses, indicating that
facultative scavengers cannot replace obligate vertebrate scavengers
completely (Hill \emph{et al.} , 2018). Yet, in other ecoregions, the
decline of top predator and scavenger (Tasmanian devil \emph{Sarcophilus
harrisii} ) or exclusion of dominant scavengers resulted in higher
detection and utilization of carcasses by meso-predators,
notwithstanding increased persistence time and availability of carrion
to decomposers (Cunningham \emph{et al.} , 2018; Tobajas \emph{et al.} ,
2021). Thus, the loss of apex vertebrate scavengers may elicit
differential responses in scavenging communities and carrion persistence
between eco-regions. Although rapid removal of carrion by vertebrates
was a consistent finding of the above studies, they became less
efficient in handling carrion at high carrion densities mimicking Mass
Mortality Event (\textgreater{}350kg/20 m\textsuperscript{2}) that led
to reduced nutrient cycling, die-offs of vegetation and trees due to
nutrient overload, and subsequent introduction of new plants in the area
(Tomberlin \emph{et al.} , 2017). As scavengers and decomposers compete
for carcasses, Devault \emph{et al.} (2004) found that contribution of
vertebrates in removing carrion reduced and that of decomposers
increased with increasing ambient temperature, indicating an
environment-dependent outcome of such competition. However, studies that
compare carrion removal rates between scavenger types and decomposers
are lacking.

Our experimental study attempts to understand carrion removal in a
forested landscape of Central India, by estimating the utilization of
carrion by vertebrate scavengers compared to invertebrates, microbes
(decomposers), and moisture loss (control). We addressed this question
by placing chicken carcasses under uniform environmental conditions in
four experimental set-ups that excluded either or all of the scavenging
guilds (i.e. vertebrates, invertebrates, microbes and control). We
measured daily carcass biomass to compare removal rates between
scavenging guilds using linear mixed effect models. Our study showed
that vertebrate scavengers contributed to maximum carrion removal per
day, followed by invertebrate scavengers, and microbial decomposition.

Methods

\section*{Study Area}

{\label{study-area}}

We carried out this study in the buffer area of Panna Tiger Reserve,
Madhya Pradesh, India in April 2019. The dominant vegetation is dry
deciduous forests interspersed with grassy meadows. The region has a
tropical climate with mean summer temperatures between 24-40 °C. Summers
are dry with mean rainfall of 6 mm in April. The rugged land features of
the Park -- plateaus and gorges -- along with tall large trees provide
suitable nesting and roosting sites for several vulture species
(Red-Headed Vulture \emph{Sarcogyps calvus} , White-rumped
Vulture\emph{Gyps bengalensis} , Long-billed Vulture \emph{Gyps indicus}
, Egyptian Vulture \emph{Neophron percnopterus} , Griffon
Vulture\emph{Gyps fulvus} , Himalayan Griffon \emph{Gyps himalayensis} ,
and Cinereous Vulture \emph{Aegypius monachus} ) that along with the
striped hyena (\emph{Hyaena hyaena} ) are the obligate scavengers of
this system. The study area supports other meat-eating animals such as
the tiger (\emph{Panthera tigris tigris} ), leopard (\emph{Panthera
pardus} ), sloth bear (\emph{Melursus ursinus} ), jungle cat
(\emph{Felis chaus} ), golden jackal (\emph{Canis aureus} ), wild pig
(\emph{Sus scrofa} ) and several smaller mammals which also often
scavenge. Herbivores which constitute natural prey and carrion in the
Park include spotted deer (\emph{Axis axis} ), Sambar (\emph{Rusa
unicolor} ), Nilgai (\emph{Boselaphus tragocamelus} ) Indian gazelle
(\emph{Gazella bennettii} ) and four-horned antelope (\emph{Tetracerus
quadricornis} ), in addition to domestic cattle (\emph{Bos taurus} ).

Experimental Method

To observe the effects of different scavenging guilds (microbial,
invertebrate, and vertebrate) on carcass consumption and decay, we
conducted an experiment using fresh chicken carcasses (1-2 kg) (Figure
1). To control for other confounding factors that can influence carcass
persistence rates, we placed all carcasses in similar conditions --
under shade of dry deciduous vegetation with similar canopy cover and
horizontal cover (scrub/herbaceous layer density). The above conditions
ensured consistency in scavenger composition and similarity in carrion
discovery rates. The experimental control and treatments were as
follows:

\begin{enumerate}
\tightlist
\item
  Control (for estimating moisture loss): Carcasses with guts removed to
  prevent decay due to gut bacteria (n=3) were treated with
  antimicrobial agent (Neosporin in powder form) on the outside and
  inside of the body cavity, placed in a cloth sack and hung in a cage
  to exclude invertebrate and vertebrate scavengers. These were weighed
  daily to record moisture loss in the absence of microbial
  decomposition.
\item
  Microbial decomposition: Whole carcasses (n=3) were placed in cloth
  sacks to exclude invertebrate scavengers, and placed in a wire cage to
  exclude vertebrate scavengers. These were weighed daily to record loss
  of biomass due to microbial decomposition as well as by desiccation.
\item
  Invertebrate scavenging: Carcasses were placed inside wire mesh cage
  on the ground with no cloth covering, to allow invertebrate scavengers
  but to exclude vertebrate scavengers (n=6). These were weighed daily
  to record invertebrate scavenging, microbe decomposition, as well as
  moisture loss.
\item
  Vertebrate scavenging: Carcasses were weighed and staked in the open
  and monitored with camera traps to observe scavenging by vertebrate
  scavengers (n=5). All carcasses were placed in the day time, before
  noon, to give equal opportunity to avian and mammalian scavengers, as
  mammals may also be active at night but avian scavengers were active
  only in the day time. All carcasses were weighed at the time of
  placement and then daily, to measure biomass loss due to scavenging by
  vertebrates, invertebrates, microbes and by desiccation (figure 2).
\end{enumerate}

\subsubsection*{Analytical Methods}

{\label{analytical-methods}}

Proportion of biomass remaining was calculated daily for each carcass.
To observe the effects of each `treatment' (control, microbe,
invertebrate, vertebrate) on biomass removal, Linear Mixed Effect Models
(LMEs) were used to account for the correlated nature of the data,
arising from observing the same carcass over time. We modelled
logit-transformed (log-odds of) proportional biomass remaining over days
against treatment types as fixed effects, and the carcass replicate as
random effect. We modelled both additive (time + treatment) and
multiplicative (time x treatment) models to find the best fit. An
additive model implies that both time and treatment types have
independent effects on the loss of carrion biomass, and the resulting
graph would have parallel lines for each treatment type. However, a
multiplicative model points to an interactive effect between time and
treatment on the loss of carrion biomass, which would more closely
approach a natural system.

Logit-transformation allowed biomass persistence to be modelled as a
logistic function and constrained the predicted values between 0 and 1.
Proportion of carcass remaining on day 0 was considered as 0.9999, to
avoid the transformed value from becoming infinity. All analysis was
carried out in R (R Core Team, 2021). Inferences were based on the least
Akaike Information Criterion (AIC) model, which was used to predict
carcass persistence over time for different treatments.

We examined the effects (slopes) of each treatment on the decay rate of
carcass over time using `lstrends' and `pairs' functions in `emmeans'
package of R (Lenth, 2021). However, the effects thus estimated
were\emph{compounded effects} as the treatments were nested. Vertebrate
scavenging included some carcass weight loss due to invertebrate
scavenging, microbial decomposition, and water loss; whereas,
invertebrate scavenging included some microbial decomposition and water
loss. Hence, to tease apart the individual effects of scavenger guilds
on carrion removal rates, we subtracted a) the daily mean carcass weight
loss due to evaporation (estimated from control experiment) from the
daily proportional carcass weight in the microbes treatment, b) the
daily mean weight loss due to microbial decomposition from the daily
proportional carcass weight in the invertebrate treatment, and c) daily
mean carcass weight loss in invertebrate treatment from the daily
proportional carcass weight in vertebrate treatments. The above
modelling exercise was repeated on these adjusted measurements, to
estimate \emph{individual effects} of each treatment. Graphs were
generated using `ggplot2' package in R (Wickham, 2009).

\section*{Results}

{\label{results}}

A total of 17 chicken carcasses were used for carrion removal
experiments. Control carcasses persisted and were monitored up to 15
days), microbe treatment carcasses up to 14 days, and invertebrate
treatment carcasses up to 12 days. Carcasses placed for vertebrate
consumption were removed by scavengers within one day of carcass
placement. The proportion of carrion biomass remaining over time
differed between treatments (figure 2). Comparison of hypothesis found
maximum support for the interactive effect of time and treatment on
carrion removal rate. Model parameter estimates indicated fastest
removal of carcass under vertebrate scavenging followed by invertebrate
scavenging, and negligible difference in carrion loss rates between
decomposition and evaporation.

The parameter estimates of the best model showing individual effects of
treatments on logit-transformed proportional loss of carrion biomass
(Table 1) represent the logit-transformed proportional loss of carrion
biomass each day under the different treatments. The inverse
logit-transformations of these estimates gives us the change in
proportion of carrion biomass each day, while the negative sign connotes
a loss in biomass. For example, with each passing day, proportion of
carrion biomass reduces by 0.99 due to vertebrate scavenging (Time x
vertebrate scavenging) (Table 1). For invertebrate scavenging,
proportion of carrion lost each day is 0.5, and it is 0.51 for microbial
decomposition. Daily loss of carrion biomass due to evaporative moisture
loss alone (Control) was estimated at 3.6\%. Besides this, microbial
decomposition \emph{per se} resulted in 3.8\% loss of carrion biomass
and invertebrate scavengers \emph{per se} resulted in 7.3\% loss of
carrion biomass daily. In contrast, vertebrate scavengers \emph{per
se}resulted in 83\% loss of carrion biomass per day. The compounded
effect of vertebrate scavenging along with invertebrate scavenging and
microbial decomposition caused 99.9\% carrion removal in a day (Table
2).

\section*{Discussion}

{\label{discussion}}

There is little information on carrion removal rates by various carrion
feeders in tropical forests. Although limited by sample size, our
experiments allowed direct comparison of carrion removal rates between
vertebrates, invertebrates, and microbes. After adjusting for carrion
losses to other treatments, vertebrate scavengers removed carrion much
faster than did invertebrates and microbes (figure 4). However, the
daily removal of 83\% of biomass by vertebrates was for carcass less
than 2 kg, and removal rates would likely decrease with larger
carcasses, as scavengers could potentially reach satiation. Nonetheless,
the study showed drastic differences in carrion removal rates between
taxa, and indicated the irreplaceable role of vertebrates in the
scavenging community of tropical forests, without whom carcasses
persisted over prolonged time periods. Thus, our results support earlier
studies that found overwhelming influence of vertebrate scavengers on
carrion removal compared to other scavenging / decomposing guilds
(Devault, Brisbin and Rhodes, 2004; Cunningham \emph{et al.} , 2018).

With vertebrates removing a majority of carcass biomass in a short time,
most of the nutrients were retained and recycled in the biosphere.
Vertebrate scavengers consumed chicken carcasses completely, down to the
bones and skin. Invertebrates removed only the soft tissue, leaving the
bones, skin and feathers behind. This would need to be mineralised by
microbes or consumed by vertebrates to re-enter the biotic sphere.
Vertebrate consumption ensures that these minerals -- particularly
calcium from bones -- is at least partly retained in the biotic sphere,
instead of its slow loss into abiotic environment, thereby playing an
important ecosystem function. Quantitative studies on nutrient cycling
through scavenging are rare (Barton \emph{et al.} , 2013;
Macdonald\emph{et al.} , 2014), and little is known about the
proportions of nutrients absorbed into scavengers from carrion and
thereby retained within the biosphere. We can assume that nutrient
retention from carrion to scavengers would follow Lindeman's `Ten
Percent Law' of energy transfer between trophic levels (Lindeman, 1942;
Brown and Gillooly, 2003). This would likely differ between tropical and
temperate regions, with nutrient cycling likely much faster in tropical
regions than in temperate regions where cold climate may inhibit
microbial action. Very few studies have examined the bioenergetics of
carrion so far, with some exceptions (Putman, 1978).

Although invertebrates remove carrion at a slower rate than vertebrates,
they do play an important role in decomposition of carcasses and
nutrient cycling (Coleman and Hendrix, 2000). Exclusion of invertebrates
from a carcass for the initial days decelerated carcass decomposition by
several days (Pechal \emph{et al.} , 2013). Thus, even in the paucity of
vertebrate scavengers, nutrient recycling will be continued by
invertebrate scavengers, but at a slower rate in a tropical dry
deciduous forest system. Little is known about invertebrate scavenging,
as a process. Future studies are required on succession in invertebrate
community as the carrion decomposes, interactions with microbes during
carrion decomposition, and if carrion removal rates are influenced by
the diversity of invertebrate scavengers. Putman (1978) found that most
of the carrion in the form of mouse carcasses was removed by blowfly
larvae, among invertebrates. Another study found that carcass size and
type of carrion influenced the dipteran community (Kneidel, 1984). Only
two dipteran species which were more specialised with respect to season
were found on mouse carrion, while a greater number of dipteran species
which were less season-specific consumed other types of carrion.

Besides the quantification of carrion removal rate by different groups,
our study yielded many qualitative observations which can contribute to
the understanding of carrion natural history. When invertebrates were
not excluded from carcasses, flies discovered carrion within a few hours
and laid eggs. Maggots hatched after two to three days and consumed most
of the carrion over a period of several days if vertebrates were
excluded. Some beetles were also observed on/around carcasses but in
less numbers than flies and their larvae. Feathers and skin slowed down
their consumption; most of the consumption took place where the skin or
flesh was exposed to invertebrates. When vertebrates were not excluded,
several species visited carcasses such as the Red-Headed Vulture,
Egyptian Vulture, Striped Hyena, and Leopard (Figure 3). These species
were amongst the first to discover and consume carcasses. Other species
which visited the carcass, but subsequently, were Wild Pigs, Ruddy
Mongoose, Golden Jackal and Indian Fox. Most scavenging by mammals took
place after sunset, while scavenging by vultures was entirely during the
day.

Among obligate scavengers, the critically endangered Red-headed Vultures
were the most photocaptured at the experimental carcasses followed by
Egyptian Vultures. Considering their size, chickens might be predicted
to be too small for these vultures. However, as many as five red-headed
vultures -- normally found in pairs or solitarily -- were captured
feeding on a single chicken carcass (Figure 3). Three of these appeared
to be juveniles. Interestingly, a goat carcass placed nearby -- although
not at the same time -- was not visited by any vultures at all. This
could be due to random chance, or because of some difference in
detectability. For example, the bright white feathers of the chicken
might be more noticeable for a gliding vulture than a dark-coloured
goat. An experiment to control for these factors with respect to
detection of carcasses may reveal more. Among the species that were not
captured at carcasses in the experiment, but were present at other
carcasses or sighted in the area include Tiger, Cinereous Vulture,
Jungle Cat, and Common Palm Civet.

Our findings, especially the estimates of carrion removal rates, could
have been influenced by several ecological factors that were beyond the
control of this experiment. Relative abundance of vertebrate scavenger
species would influence carrion removal rates; e.g., carrion removal
rates might differ between the study area and a different forest with
fewer vultures but higher numbers of top and meso- mammalian predators.
Carcass size is another important factor. Removal rates would have
slowed down if larger carcasses such as goats or cattle were used, as
individual scavengers that discovered the carcass became satiated.
Further, invertebrate scavengers might take advantage of such larger
resources and respond numerically due to their shorter generation times
and thereby contribute more to carcass removal than currently estimated.
We account for moisture loss by desiccation under natural conditions,
and as seen in Fig. 2, moisture loss was a function of ambient humidity
and temperature, on day five of the treatment there was mild rain and
the carcasses gained weight. Whilst there was a non-significant
difference in removal rates between microbes and control (evaporative
moisture loss) (Table 2), this could imply that either microbes
contributed negligibly to the removal of carrion, or the anti-microbial
treatment in our control samples was not effective in reducing microbial
activity and our estimates of moisture loss was compounded by some
microbial losses. However, this issue does not affect the comparison of
carrion removal rates between vertebrates and invertebrates. Our
experiment spanned a single season (early summer) and did not capture
seasonal variations in environmental conditions that could influence
relative contribution of scavenger groups, and the absolute removal
rates. Our sample size was also small that might have resulted in large
variability in proportional weight of carcasses over time (Figure 2).

Whilst our field experiment provided some insights, many questions
remain to be answered to further our understanding of carrion ecology in
tropical forests. a) Effects of relative abundance of different species
in the scavenging assemblage on carrion utilization (Huijbers \emph{et
al.} , 2016; Morales-Reyes \emph{et al.} , 2017; Naves-Alegre \emph{et
al.} , 2021), b) succession of scavenging groups on carrion, c)
influence of carrion size on the richness, abundance, composition and
succession of scavenger community are some of these questions. Our
experimental approach and inferences can form the foundation on which
studies investigating the above questions can be developed.

Figure Legends

Figure 1: Experimental setup for observing carrion biomass loss due to
different treatments (Clockwise from Top Left): 1. A chicken carcass
being weighed after exposure to invertebrate scavenging; 2. vertebrate
scavenging -- carcasses were placed in the open and monitored through
infrared camera traps; 3. invertebrate scavenging -- carcasses were
placed in a wire cage to exclude vertebrate scavenger; 4. microbial
activity -- carcasses were placed in cloth bags and hung in a wire cage
to exclude invertebrates and vertebrate scavengers. Control carcasses
were also placed similarly after treatment with an antimicrobial agent.

Figure 2: Boxplot showing distribution of proportional carcass biomass
remaining over days for each treatment.

Figure 3: Some vertebrate scavenger species captured at experimental
carcasses. Clockwise from top left - Red-headed Vulture (\emph{Sarcogyps
calvus} ), Egyptian Vulture (\emph{Neophron percnopterus} ), Golden
Jackal (\emph{Canis aureus} ), Leopard (\emph{Panthera pardus} ), Indian
Fox (\emph{Vulpes bengalensis} ), Striped Hyena (\emph{Hyaena hyanea} ).
Bottom: A group of Red-Headed Vulture and an Egyptian Vulture feeding on
an experimental chicken carcass.

Acknowledgements

We would like to thank the Chief Wildlife Warden, and Chief Conservator
Forests of the Madhya Pradesh Forest Department for granting permissions
to carry out the field work. We thank the L. Krishnamurthy, Field
Director Kanha Tiger Reserve, K.S. Bhadoria, Field Director of Panna
Tiger Reserve, and the Madhya Pradesh Forest Department Staff , for all
their support and facilitation. We thank the Director, Dean, Course
Director and Assistant Course Director of XVI MSc Course, and faculty at
WII. The field work was funded by a grant from Raptor Research and
Conservation Foundation (RRCF) and facilitated by Kiran Srivastava.
Bruce Marcot is thanked for useful comments on the study proposal. BI
gratefully acknowledges the following field assistants and forest
department staff for their assistance: Kanhaiya, Nirottam, Sampat,
Suraj, and Manjula in Kanha, and Lal Singh and the tiger tracking teams
of Panna. BI thanks XVI MSc students, and Shravana, Jayant, Anjali,
Manish, Pratik, Ujjwal and Neha, K Ramesh and his team, particularly
Deepti, Kamna, Supratim and Darshan for assistance and facilitation.

Author Contributions

BI -- Study design, funding acquisition, data collection, analysis,
Writing---Original Draft. YVJ -- Study design, methodology, review and
editing, supervision, funding acquisition. SD - Study design,
methodology, review and editing, supervision. QQ - Study design,
methodology, supervision.

Data Accessibility

The authors confirm that the data supporting the findings of this study
are available in the appendix and on FigShare.

Funding

This work was conducted by BI as part of a dissertation for the award of
a Master's degree in Wildlife Science from Saurashtra University,
through the Wildlife Institute of India. It was funded by the Wildlife
Institute of India and the Raptor Research and Conservation Foundation
(RRCF).

Competing Interests

The authors declare no competing interests.

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{\label{references}}

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Table 1. Parameter estimates of the best model showing individual
effects of treatments on logit-transformed proportional loss of carrion
biomass.\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
\textbf{Variables} & \textbf{Estimate} & \textbf{SE}\tabularnewline
Time & -0.19 & 0.03\tabularnewline
Microbial decomposition & 0.41 & 0.45\tabularnewline
Invertebrate scavenging & 1.64 & 0.44\tabularnewline
Vertebrate & 2.98 & 0.53\tabularnewline
Time x microbial decomposition & -0.05 & 0.06\tabularnewline
Time x invertebrate scavenging & -0.02 & 0.06\tabularnewline
Time x vertebrate scavenging & -5.88 & 0.65\tabularnewline
\bottomrule
\end{longtable}

Table 2: Mean (SE) carrion removal rates, estimated as daily
proportional weight loss of carcass under different treatments, with
95\% CI.\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\textbf{Treatment} & \textbf{Mean Carrion Removal Rate (SE)} &
\textbf{Upper Confidence Interval} & \textbf{Lower Confidence
Interval}\tabularnewline
Control (evaporative water loss) & 0.036 (0.0024) & 0.041 &
0.031\tabularnewline
Microbial decomposition & 0.039 (0.003) & 0.08 & 0.066\tabularnewline
Invertebrate scavenging & 0.073 (0.004) & 0.045 & 0.033\tabularnewline
Vertebrate scavenging & 0.833 (0.043) & 0.919 & 0.749\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-1/Figure-1}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
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\includegraphics[width=0.70\columnwidth]{figures/Figure-2/Figure-2}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-3/Figure-3}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Appendix-Figure-1/Appendix-Figure-1}

\end{center}
\end{figure}

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