Cost, effort and outcome of mammal rediscovery: Neglect of small species

Abstract

There is often intense public interest in the process of rediscovery of species that were presumed extinct, although rediscovered mammals are typically small, inconspicuous inhabitants of tropical forests. Conservation actions for small species are relatively inexpensive compared to the interventions required to protect charismatic, large mammals. However, threatened small mammals such as rodents, bats, shrews and small marsupials attract less research attention, conservation actions, space in zoos, and funding than larger species, and most threatened small mammals receive no attention, particularly those in tropical forest habitats. I investigated how the body size of rediscovered mammals has changed during the last century, how body size is associated with search and conservation effort and subsequent recovery, and the success of recovery actions for rediscovered mammals. There has been a strong decline in the mean body size of rediscovered mammals since the 19th century. Smaller species were missing for longer before rediscovery, and attracted less search effort. Cost estimates were lower in recovery plans for smaller rediscovered mammals. Despite this, increasing population trend after rediscovery was associated with larger body size, and larger species recovered better with conservation effort, although small species declined despite conservation effort. All species with no conservation actions (the majority of small species) were declining. Sixty percent of rediscovered mammals remain critically endangered or endangered, and 8% (6 species) are likely to be extinct. I argue that conservation outcomes for rediscovered mammals could be greatly improved by a modest increase in attention to small-bodied species.

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Cost, effort and outcome of mammal rediscovery: Neglect of small species
Diana O. Fisher
⇑
The University of Queensland, School of Biological Sciences, St. Lucia, 4072 Queensland, Australia
article info
Article history:
Received 3 January 2011
Received in revised form 2 March 2011
Accepted 8 March 2011
Available online 1 April 2011
Keywords:
Rediscovery
Mammal extinction
Recovery plan
Body size
Captive breeding
abstract
There is often intense public interest in the process of rediscovery of species that were presumed extinct,
although rediscovered mammals are typically small, inconspicuous inhabitants of tropical forests. Con-
servation actions for small species are relatively inexpensive compared to the interventions required
to protect charismatic, large mammals. However, threatened small mammals such as rodents, bats,
shrews and small marsupials attract less research attention, conservation actions, space in zoos, and
funding than larger species, and most threatened small mammals receive no attention, particularly those
in tropical forest habitats. I investigated how the body size of rediscovered mammals has changed during
the last century, how body size is associated with search and conservation effort and subsequent recov-
ery, and the success of recovery actions for rediscovered mammals. There has been a strong decline in the
mean body size of rediscovered mammals since the 19th century. Smaller species were missing for longer
before rediscovery, and attracted less search effort. Cost estimates were lower in recovery plans for smal-
ler rediscovered mammals. Despite this, increasing population trend after rediscovery was associated
with larger body size, and larger species recovered better with conservation effort, although small species
declined despite conservation effort. All species with no conservation actions (the majority of small spe-
cies) were declining. Sixty percent of rediscovered mammals remain critically endangered or endangered,
and 8% (6 species) are likely to be extinct. I argue that conservation outcomes for rediscovered mammals
could be greatly improved by a modest increase in attention to small-bodied species.
Ó2011 Elsevier Ltd. All rights reserved.
1. Introduction
More than a third of mammal species that have been classified
as extinct, possibly extinct, or flagged as missing, have been redis-
covered. These rediscovered mammals were all last recorded
between the 1820s and the present (Fisher and Blomberg, 2011).
Many missing species have a high scientific or public profile
(Roberts et al., 2010; Scott et al., 2008), although the majority of
rediscovered mammals are inconspicuous (Fisher, 2010; Fisher
and Blomberg, 2011). Fisher and Blomberg (2011) analyzed data
on rediscovery rates of purportedly extinct mammals since 1500,
to determine which traits affect the probability of rediscovery.
They found that body size did not independently predict rediscov-
ery rate, although persecuted and harvested species are predomi-
nantly large and conspicuous (Fisher and Owens, 2004; Isaac and
Cowlishaw, 2004; Owens and Bennett, 2000), and these tended
to be rediscovered more frequently in the 20th century (Fisher
and Blomberg, 2011). Mammals that declined due to habitat loss
were also rediscovered relatively frequently, unless they had very
restricted ranges. Species affected by habitat loss are most likely
to be small-bodied endemics, especially in tropical forests (Bennett
and Owens, 2002; Fisher, 2010; Fisher and Owens, 2004; Owens
and Bennett, 2000). Fisher and Blomberg (2011) showed that a
few charismatic, large, missing mammals have been the focus of
disproportionately high, but unsuccessful search effort, but most
missing mammals received little or no attention.
We might expect that this lack of attention would be reflected
in lower search effort, a longer time to be rediscovered, less fund-
ing for searches, fewer conservation actions and therefore a rela-
tively poor chance of recovery of uncharismatic species after
rediscovery, because there is substantial published evidence of
bias in favor of large species conservation. Amori and Gippoliti
(2000) found that globally, rodents, bats, insectivores, and most
small marsupials were severely under-represented in published
single-species conservation studies of mammals, relative to the
proportion of threatened species in these orders. The proportion
of threatened insectivores, microchiropterans and rodents in cap-
tive breeding programs is tiny (61%), in contrast to large-bodied
groups such as primates, carnivores and ungulates (Balmford
et al., 1996). Sitas et al. (2009) concluded that 75% of threatened
mammals receive no conservation actions, and that the orders
Insectivora, Didelphimorphia (South American marsupials), Roden-
tia and Chiroptera have the least conservation effort. Small rodents,
bats, shrews and marsupials typically use cryptic behavior to avoid
predators, are nocturnal, often solitary and arboreal, and can only
0006-3207/$ - see front matter Ó2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biocon.2011.03.005
⇑
Address: School of Biological Sciences, Goddard Building (8), The University of
Queensland, St. Lucia, 4072 Queensland, Australia. Tel.: +61 7 33469004; fax: +61 7
33651655.
E-mail address: d.fisher@uq.edu.au
Biological Conservation 144 (2011) 1712–1718
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be observed by specialist trapping methods (Sutherland, 2003).
Such mammals have a low public profile (Sitas et al., 2009), and
species identification often requires expert knowledge, so fewer
potential searchers are able to recognise them. Conversely, large
mammals attract the most public interest, research attention, rep-
resentation on Species Survival Commission specialist groups, and
conservation funding (Amori and Gippoliti, 2000; Gimenez-Dixon
and Stuart, 1993; Magin et al., 1994; Metrick and Weitzman,
1996; Sitas et al., 2009; Ward et al., 1998). Gimenez-Dixon and
Stuart (1993) found that in the 10 years after the development of
the first Species Survival Commission action plans, more projects
suggested in action plans were implemented for taxonomic groups
containing large species (e.g. elephants: 156 projects, cetaceans: 24
projects, mustelids and viverrids (small-bodied carnivorous mam-
mals): six projects). Large mammals were the most likely taxa to be
listed by the US Endangered Species Act in the early 1990s (Metrick
and Weitzman, 1996). Recently, Sitas et al. (2009) showed that
large-bodied, well-known and charismatic mammals still receive
the majority of conservation actions globally. Metrick and
Weitzman (1996) found that body size and taxonomic group were
the main determinants of conservation spending in the USA. Large
species and mammals were favored. The authors interpreted this
to mean that conservation attention was focused on species that
are most attractive to us, because they most resemble humans.
In agreement with the idea that large species are valued dispropor-
tionately by conservation managers, Balmford et al. (1996) found
that zoos prioritize exhibition and breeding of large vertebrates,
although threatened species far outnumber the space and
resources available for captive breeding. Attractiveness and body
size are also the main determinants of the size of other captive
vertebrate populations (the number of individuals in captivity),
such as snakes (Marešová and Frynta, 2008).
Balmford et al. (1996) suggested that bias towards large species
results in inefficient use of conservation resources, because small-
bodied taxa are more likely to breed well in captivity, and are
cheaper to maintain in appropriate numbers for genetic manage-
ment. Larger carnivores are more likely to show abnormal behavior
and signs of stress in captivity (Clubb and Mason, 2003), and
breeding programs for the smallest mammals cost around a tenth
of those for the largest (Balmford et al., 1996). Small mammals in
tropical regions are least likely to receive conservation attention,
and most receive none (Sitas et al., 2009), despite conservation ac-
tions such as habitat protection being cheapest to implement in
these regions (Balmford et al., 2003), and the smaller area of hab-
itat required by small species (Fisher and Owens, 2004). Reduced
spending on conservation measures presumably increases extinc-
tion risk (Brooks et al., 2009; Joseph et al., 2009), and this effect
is expected to be acute in newly-rediscovered species, which are
by definition very close to extinction. Lack of interest in rediscov-
ered small mammals is therefore predicted to lead to continued
decline and rapid extinction of many of these species. In this paper,
I investigate how and why mean body size of rediscovered
mammals has changed over time, how body size has influenced
the effort devoted to rediscovery and subsequent recovery of miss-
ing mammals, and the success of recovery efforts. I interpret con-
servation outcomes in the context of searcher expertise and
funding.
2. Methods
2.1. Data and definitions
I compiled a global database of species that have published ac-
counts of rediscovery or attempted rediscovery (see Fisher and
Blomberg, 2011). I established the status and detection history of
these species using past and present IUCN red lists and related
publications, primary literature, books, and the Committee on Re-
cently Extinct Organisms mammal database (MacPhee and
Flemming, 1999). I obtained population trend data (ranked -1 for
declining, 0 for stable, and 1 for increasing), conservation status
categories, and recovery actions from the present IUCN red list
and published species recovery plans. I ranked recovery actions
as follows: the species occurs in a minimally-managed or unman-
aged reserve = 1, an actively managed reserve = 2, captive breed-
ing = 2, translocation = 2, and listing/legal protection only = 0. I
summed the action ranks for each species to obtain an index of
recovery effort. I determined the identity of searchers and their
institutions from these publications, and from accounts in Bille
(1995, 2006) and Shuker (1993). I assigned a searcher institution/
profession in 13 categories: museum researcher, zoo employee,
amateur naturalist, professional scientific society, farmer, environ-
mental consultant, construction worker, government agency,
university faculty, postgraduate student, wildlife photographer,
hunter, or non-government conservation organization.
I determined sources of funding for searches from the acknowl-
edgements sections of papers, and divided these into nine catego-
ries: self-funded, museum, zoo, amateur natural history society,
government agency, university, private industry, grant funding
body, or non-government conservation organization. I contacted
individual searchers directly to obtain estimates of the cost of
mounting particular search expeditions (except in the case of the
kouprey Bos sauveli, which had search cost estimates included in
a recovery plan). The total cost of expeditions did not include sal-
ary. I determined the estimated cost of species recovery for 5 years
from the most recent available published species recovery plans
which included detailed costings. I converted currency to US dol-
lars by using contemporary exchange rates, then converted be-
tween years to account for inflation using a US gross domestic
product deflator index based on the International Monetary Fund
(2010). For each species, I recorded body mass (g), and traits likely
to be associated with body mass: the threat associated most with
decline, and ranked geographic range size. A main threat was as-
signed if one threat was reported to be the major one, either hab-
itat loss (deforestation, agricultural clearing, fragmentation,
degradation, overgrazing), overkill (harvesting, hunting, exploita-
tion, persecution or bycatch) or introduced species (invasive pre-
dators or diseases). I recorded geographic range rank (range with
a precision of one order of magnitude; 1 = up to 1 km
2
,2=1–
10 km
2
, 7 = 100,000–1000,000 km
2
)(Fisher and Blomberg, 2011).
For rediscovered species, the index of search effort was the
number of reported search expeditions targeted to the species after
it was reported missing, and before it was rediscovered. I also used
the number of searches targeted to species that remain missing or
extinct after their last sighting, in order to test for a correlation be-
tween search effort and body size (data from Fisher and Blomberg,
2011).
2.2. Statistical analysis
I used linear models in R (R Development Core Team, 2010)to
test for associations between the date of rediscovery and (log) body
mass; last sighting date and (log) body mass; the interval between
last sighting date and rediscovery and (log) body mass; search effort
and (log) body mass of missing species; search cost and (log) body
mass, (log) former range size, distance between the home institu-
tion of the searcher and the rediscovery site, and local versus over-
seas location of searchers; estimated cost of recovery and (log) body
mass, threat, (log) former range size, the interval between last sight-
ing date and rediscovery, or discovery/species description date; the
index of recovery effort and (log) body mass, population trend ver-
sus (log) body mass and index of recovery effort. I used an anova in R
D.O. Fisher/ Biological Conservation 144 (2011) 1712–1718 1713

Author's personal copy
to test if mean rediscovery date varied according to the profession of
rediscoverers, and separate anovas to test if mean rediscovery date
varied with funding source, and to test if mean (log) body mass var-
ied with profession of rediscoverers or funding body. I used Tukey
HSD post hoc tests to determine where significant differences were
in these overall models. Because multiple searchers usually contrib-
uted to the rediscovery of each species, and multiple funding bodies
supported each rediscovery, each species could be represented
more than once in this analysis.
I did not use statistical models to account for phylogenetic non-
independence, because previous analyses of this dataset have
shown that phylogenetic signal in the traits associated with redis-
covery (including body mass) is very weak or non-existent. In pre-
vious analyses, there was no significant difference between any of
the phylogenetic and non-phylogenetic linear model results
(P> 0.99 in each case). This is probably because rediscoveries are
scattered across families and genera of mammals, rather than
being clumped in certain phylogenetic lineages (Fisher, 2010;
Fisher and Blomberg, 2011).
3. Results
During the last century, there has been a strong, progressive de-
cline in the mean body size of rediscovered mammals (F
1,60
= 11,
p= 0.001). This is not due to an increase in the proportion of redis-
covered species affected by habitat loss relative to the number of
species affected by overkill; there was no significant change in
the mean category of threat affecting mammals that are rediscov-
ered (overall model with date as the dependent variable, and
logged species body mass and threat type as interacting indepen-
dent variables, F
5,60
= 3.4, p= 0.009), and no interaction between
threat and body size in this model (Fig. 1). The change in body size
of rediscovered mammals was not a reflection of any decline in the
mean body size of presumed-extinct species since 1820 (the pool
of species from which rediscoveries are made); there was no signif-
icant association between the last sighting date of extinct mam-
mals since 1820 and body mass (F
1,73
= 0.9, p= 0.35). Larger
species were also missing for significantly shorter periods of time
before rediscovery (F
1,64
= 5.7, p= 0.02). Missing mammals have
predominantly been rediscovered by museum researchers and uni-
versity academics (Fig. 2a). Together, these two professions ac-
count for nearly half of all people making mammal rediscoveries
globally (45/99 searchers). A substantial number of missing species
have also been found by employees of government environment
departments, non-government conservation organizations (NGOs)
and amateur natural historians. Only 10% of people involved in
mammal rediscoveries were not in a profession that requires bio-
logical training (two construction workers in a National Park, three
wildlife photographers, one hunter, and four farmers). There has
been no obvious change in the level of expertise of searchers, but
there has been a change in the relative roles of museum research-
ers and university academics in mammal species rediscovery dur-
ing the last century. The mean date of rediscovery for species found
by museum employees (the late 1960s) is earlier than the mean
date of species found by university academics and conservation
NGOs (the 1990s) (Fig. 2a, F
12,86
= 2.2, p= 0.018, Tukey post hoc
test: difference between academics and museums, p= 0.03,
difference between NGOs and museums, p= 0.03). Rediscovery of
missing mammals has predominantly been funded by museums,
non-government conservation organizations, and government
departments, which together account for 47% of funding sources
(Fig. 2b). A substantial minority of rediscoveries (15%) have also
been entirely self-funded by individuals. There has been a trend to-
wards greater funding by NGO’s, charities and private industry
from the late 1980s to the present, with fewer rediscoveries tend-
ing to be self-funded by individuals, or funded by museums than in
the 1960s and 70s. (F
8,93
= 2.4, p= 0.02, Tukey post hoc test: differ-
ence between NGOs and self, p= 0.06, difference between NGOs
and museums, p= 0.015). Although the profession of searchers
and the sources of funding have changed during the last century,
this did not explain why mean body mass of rediscovered species
has declined. Searcher profession and funding source were not
associated with mean body mass of rediscovered species
(F
12,86
= 0.6, p= 0.86 and F
8,93
= 1.5, p= 0.17, respectively). Species
Fig. 1. Decline in body mass in rediscovered mammals between 1900 and 2010, with respect to threats.
1714 D.O. Fisher/ Biological Conservation 144 (2011) 1712–1718

Author's personal copy
rediscovered by museum employees weighed 9131 ± 4897 g, and
those rediscovered by university researchers weighed 7627 ±
6138 g.
We were able to obtain an estimate of the cost of searching for
15 species that have been targeted by expeditions aiming to
rediscover them since 1980 (around a quarter of the number of
rediscovered species). These were: the Talaud flying fox Acerodon
humilis (successful search), kouprey B. sauveli (unsuccessful
search), Christmas Island shrew Crocidura trichura (unsuccessful
search), Machu Pichu chinchilla rat Cuscomys oblativa (unsuccess-
ful search), woolly flying squirrel Eupetaurus cinereus (successful
search), Salim Ali’s fruit bat Latidens salimali (successful search),
dibbler Parantechinus apicalis (successful search), Puebla deer
mouse Peromyscus mekisturus (unsuccessful search), Bahian tree
rat Phyllomys unicolor (successful search), Bougainville monkey-
faced bat Pteralopex anceps (successful search), Julia Creek dunnart
Sminthopsis douglasi (successful search), pygmy tarsier Tarsius
pumilus (unsuccessful search), Attenborough’s echidna Zaglossus
attenboroughi (unsuccessful search), and central rock rat Zyzomys
pedunculatus (unsuccessful search). The mean cost for three people
to search for 12 weeks (the mean effort, rounded to whole num-
bers) did not depend on the body size of the target species, or its
former range size, or the distance between the home institution
of the searcher and the rediscovery site. However, the cost of a
12 week search if the expedition organisers lived locally (in the
same country as the target species) was less than a third as much
as expeditions whose leaders travelled from another country to
search ($8970 ± 3216 versus $33,707 ± 6429, t= 2.6, p= 0.03, over-
all model F
2,12
= 5.3, p= 0.02, r= 0.62). We also repeated the
analysis using raw costs, not adjusted for inflation. The conclusions
were unchanged (non-adjusted costs for the same country:
$8696 ± 3285 versus another country: $32,541 ± 6454). The
amount spent (taking the search duration for individual species
into account), also did not depend on the body size of the target
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Museum
Naturalist
Society
Farmer
Consultant
Construction
Zoo
Faculty
Government
Photographer
Hunter
NGO
Postgraduate
Mean date
Profession / expertise
*
*
#
23
7
7
4
2 2 4 22 10
3
1
12 2
a
b
Fig. 2. Changes in the relative contribution of categories of profession involved in making and funding rediscoveries of 67 mammals between 1900 and 2010. Error bars are
standard errors. Sample sizes (number of searchers/funders) are shown above each category of profession. The number of searchers and funders is more than the number of
species, because some species were searched for by expeditions with multiple people, or more than one funding body contributed to the funding. Means with a

differ
significantly from those with a # (overall models p< 0.10). Means with the same symbol do not differ significantly from one another. (a) rediscoverers and (b) funders.
Industries are mining companies (four species), fishing (one species), airlines (two species), tea (one species) and tobacco (one species).
D.O. Fisher/ Biological Conservation 144 (2011) 1712–1718 1715

Author's personal copy
species, or its former range size, or the distance between the home
institution of the searcher and the rediscovery site. Searchers who
lived locally spent around 75% less ($5596 ± 1780 versus
$27,707 ± 4650, overall model F
1,13
= 17.7, p= 0.001, r= 0.73).
Most rediscovered species either had no recovery plans (that I
was able to locate), or had plans with no costings. I obtained the
estimated cost of recovery for 5 years from published recovery
plans for rediscovered species (n= 13, the bridled nailtail wallaby
Onychogalea fraenata, northern hairy-nosed wombat Lasiorhinus
krefftii, Leadbeater’s possum Gymnobelideus leadbeateri, Gilbert’s
potoroo Potorous gilberti, Pygmy hog Porcula salvania, Heath mouse
Pseudomys shortridgei, Sandhill dunnart Sminthopsis psammophila,
dibbler Parantechinus apicalis, Hastings River mouse Pseudomys
oralis, Cuvier’s hutia Plagiodontia aedium, Julia Creek dunnart
S. douglasi, Hispaniolan Solenodon Solenodon paradoxus, and
black-footed ferret Mustela nigripes) and two missing/extinct spe-
cies; the baiji, Lipotes vexillifer (which had a costed recovery plan
prepared in case of rediscovery, but was not rediscovered), and
the red wolf, Canis rufus (which is extinct in the wild and has a
costed recovery plan). For these 15 species, cost of recovery for
5 years was not significantly correlated with threat, former range
size, the interval between last sighting date and rediscovery, or dis-
covery date, but it was significantly associated with body mass
(F
2,10
= 8.6, p= 0.015, r= 0.59, Fig. 3). The mean estimate of recov-
ery cost over 5 years for small rodents, shrews, and small marsupi-
als (<1000 g) was approximately half a million dollars (US$
496,414 ± 168,427). The mean cost for medium-sized species (Gil-
bert’s potoroo P. gilberti, the pygmy hog P. salvania, and Leadbeat-
er’s possum G. leadbeateri) was approximately a million dollars
(US$ 11,75,133 ± 919,558). Larger species (excluding one outlier,
see below) cost around three million (US$ 29,05,455 ± 649,213).
The outlier was the black-footed ferret M. nigripes (a US species
at the low end of the medium body size category, approximately
one kilogram), which had an estimated cost of recovery of around
eleven million dollars for a 5-year recovery plan. The species with
the second highest estimate of recovery cost, the red wolf, is also a
North American mammal. Thus, a typical search using overseas
agencies to rediscover a large-bodied mammal species cost on
average 2% of the total estimated cost of recovery for 5 years,
and 7% of the total cost of recovery for small-bodied species
(e.g. rodents < 1000 g).
Around a third of missing and extinct species have not been the
targets of any documented searches, and a quarter of rediscovered
species have had no conservation actions applied to them (apart
from listing). Most rediscovered mammals (80%, not including Data
Deficient species) are declining. Few are stable (6%), or increasing
(6%). Six rediscovered species are now listed as EX or CR (tagged
as possibly EX) (8% of rediscoveries, Fig. 4). These are the desert
rat kangaroo Caloprymnus campestris, central rock rat Z. peduncula-
tus, Garrido’s hutia Mysateles garridoi, King rat Uromys rex, Christ-
mas Island shrew C. trichura, and Vanikoro flying fox Pteropus
tuberculatus. The desert rat kangaroo and central rock rat are
Australian desert mammals, and the others are tropical island
dwellers. All of these species are relatively small-bodied (4–
1600 g). The central rock rat survives in two captive populations,
and conservation actions including captive breeding and habitat
protection are underway. The only known individual of the Christ-
mas Island shrew was briefly kept in captivity for 12 months after
its rediscovery. A second individual died shortly after capture,
therefore no meaningful management, such as captive breeding,
was possible. There were no conservation actions attempted after
the rediscovery of the other extinct (and possibly extinct) rediscov-
ered species. Not including EX and CR (possibly EX) species, 60% of
rediscovered mammals are critically endangered or endangered. A
small minority (12%) are now ‘near threatened’ or ‘least concern’,
nearly all because of a change in knowledge about their status.
The three rediscovered species classified as increasing in popula-
tion size by the IUCN are two fur seals that were harvested to
near-extinction and have now substantially recovered since the
complete cessation of hunting (the Juan Fernández and the Guada-
lupe fur seal, Arctocephalus philippii and A. townsendi), and the
black-footed ferret M. nigripes (the target of extraordinary recovery
funding and effort). The index of search effort for missing species
(the number of searches documented in published reports) was
significantly but weakly correlated with body mass (F
1,185
= 9.8,
p= 0.002, r= 0.22). The index of recovery effort for rediscovered
species was not associated with body mass (F
1,65
= 1.0, p= 0.32).
However, increasing population trend after rediscovery was associ-
ated with increasing body mass (F
1,54
= 9.1, p= 0.004), more con-
servation actions taken after rediscovery (recovery effort)
(F
1,54
= 15.1, p= 0.0003), and an interaction between body mass
and actions: smaller species declined regardless of the number of
Fig. 3. Estimated cost to implement a 5-year recovery plan versus body mass of rediscovered species. The outlier ($11 M) is the black-footed ferret, Mustela nigripes.
1716 D.O. Fisher / Biological Conservation 144 (2011) 1712–1718

Author's personal copy
conservation actions, and larger species increased in population
size more if they had more conservation actions (F
1,54
= 6.6,
p= 0.01). Population trend after rediscovery was not associated
with threat or former range size.
4. Discussion
If small missing mammals do receive less conservation atten-
tion than large species, we expected the rediscovery of extant spe-
cies to be delayed, relative to larger species. We also expected that
small species would receive lower search effort, less funding for
searches, and fewer conservation actions after rediscovery than
large mammals. Most of these expectations were upheld. The strik-
ing decline in mean body size of rediscovered species since the
19th century, and the longer interval between last sighting date
and rediscovery date in smaller mammals, are consistent with less
attention to smaller species by searchers, and also with elusiveness
of small species. Fisher and Blomberg (2011) found that moderate
search effort increased the probability of rediscovery in missing
mammals, independently of other significant predictors such as
the cause of decline. Therefore, the lower search effort for smaller
mammals is consistent with the idea that lack of attention is re-
lated to the decline in body size of rediscovered species over time.
The body size of rediscovered species was an increasingly biased
subset of the body size distribution of missing mammals during
the last century, because there was no change in the body size dis-
tribution of the source pool of species from which rediscoveries
were made during this time (missing and extinct mammals since
1820). The declining body size of rediscovered species parallels
the pattern of declining body size in new species descriptions dur-
ing the last century. For example, Medellin and Soberon (1999)
extrapolated the relationship between description rate, taxonomy
and species characteristics to conclude that most mammals
remaining to be rediscovered will be rodents, insectivores and bats
under 100 g, and Collen et al. (2004) found that recently described
carnivores and primates are small-bodied, with small geographic
ranges. Most species recently described and remaining to be
discovered are from tropical forest areas of high endemism in Asia,
South America, Oceania and Africa, and are likely to be threatened
by habitat loss because of their small ranges (Reeder et al., 2007).
Tropical forests are also the most likely habitats in which to redis-
cover missing mammals in the future (Fisher, 2010; Fisher and
Blomberg, 2011), supporting the recent conclusions of Sitas et al.
(2009), that tropical forests are the most neglected areas globally
in terms of small mammal conservation attention.
Search costs for missing mammals were cheap. Several respon-
dents commented that their expeditions were particularly inex-
pensive, because they made a special effort to keep costs low
(e.g. by camping, and using the cheapest transport and food. For
example, Mittermeier et al. (1977) noted in their methods that
they took local buses to travel to the rediscovery site in Peru).
Although few rediscoveries were funded entirely by individuals
(especially recently, with the greater availability of NGO funding
than in the early 20th century), most were probably subsidised
by individuals, masking their true cost.
Attention given to missing mammals at the searching stage did
not appear to vary with searcher profession or expertise. We found
no evidence that rediscoveries in the early twentieth century were
made and funded by professions and groups that were more moti-
vated to seek out large, charismatic mammals than now. The
reduction in mean body size of rediscovered mammals has oc-
curred despite the relative decline in the contribution of museum
taxonomists to making and funding rediscoveries, and greater
funding contribution from NGOS, charities and private companies.
The mean body size of rediscovered species did not differ between
searcher professions or funding sources. This implies that bias to-
wards large species in conservation attention given to mammals
occurs across a range of professions, including specialist research-
ers and taxonomists. Search costs did not depend on body size, but
were much less if the searcher’s institution was in the same coun-
try as the rediscovery site. Cost efficiency seemed to be increased
by familiarity rather than decreased by travel distance, for exam-
ple, some searchers in Australia and Brazil traveled very long dis-
tances, but expeditions were still much cheaper than those of
overseas searchers.
Once rediscovered, mean estimates of the cost of recovery for
small species were a quarter of that for larger mammals. This is
probably partly because activities such as captive maintenance
cost less per individual for species with short generation times
and decreased space requirements, and small species usually need
less intensive intervention to breed well in captivity (Balmford
et al., 1996). It might also be because authors of recovery plans
underestimate the amount of money required for effective conser-
vation. They might ask for less because they are pre-empting likely
funding decisions, given that a greater share of finite funding is un-
likely to be allocated to small species at the expense of more char-
ismatic mammals (Joseph et al., 2009; Metrick and Weitzman,
1996). The finding that smaller species were more likely to show
a declining population trend after rediscovery, and larger species
benefited disproportionately from greater conservation efforts sug-
gests that recovery effort allocated to rediscovered small mammals
has often been inadequate. Rediscovered small mammals were
more likely to decline, despite the fact that global analyses have
repeatedly shown large body size to be a strong predictor of extinc-
tion risk and population loss in mammals (Cardillo et al., 2005;
Davidson et al., 2009; Fisher and Owens, 2004).
Although most rediscovered species are declining, very few
have become extinct. In agreement with the conclusions of Brooks
et al. (2009) and Rodrigues (2006), my results show that spending
and effort on conservation actions do make a significant difference
to the prospects of recovery. The index of recovery effort applied to
individual species was strongly correlated with their population
trend after rediscovery. All species with no actions were
Fig. 4. IUCN red list status of rediscovered mammals. EX = extinct, CR (EX) = crit-
ically endangered, tagged as possibly extinct, CR = critically endangered,
EN = endangered, VU = vulnerable, NT = near-threatened, LC = least concern,
DD = data-deficient.
D.O. Fisher / Biological Conservation 144 (2011) 1712–1718 1717

Author's personal copy
categorized as declining, but no actively-managed rediscovered
species subsequently became globally extinct. The rediscovered
mammal with the greatest financial investment, according to its
recovery plan (the black-footed ferret) is one of only three with
an increasing population trend. This suggests that North American
species in the dataset were at the upper end of the funding distri-
bution because their recovery cost estimates were adequate.
Searching for missing mammals is inexpensive, especially if done
by local expeditions, and is often funded by non-government
sources which do not compete with other aspects of recovery plan-
ning, such as captive breeding. Recovery actions for rediscovered
small mammals appear to be generally either lacking or under-
funded, although they are relatively inexpensive to implement. I
conclude that there is a strong potential to improve conservation
outcomes for rediscovered mammals with only a modest re-alloca-
tion of resources to include more small species.
Acknowledgments
I thank Peter Baxter for useful comments on the manuscript. I
am extremely grateful to the following who generously responded
to my questions about the cost of searching, and the status of
costed recovery plans, and provided valuable discussion and ideas:
Alan Horsup, Berry Mulligan, Brent Sewall, Chris Pavey, Chris
Walzer, Claudio Valladares- Padua, Craig Turner, Evan Bowen-
Jones, Fernando Cervantes, Ignacio De la Riva, Jeremy Bird, Jon
Riley, Jonathan Baillie, Lawrence Heaney, Louise Emmons, Luis
Darcy Verde Arregoitia, Nikki Hammond, Pablo Tete, Pat Woolley,
Paul Meek, Peter Zahler, Petra Kaczensky, Robert Dowler, Samuel
Turvey, Sharon Gursky, and Yuri Leite. This work was supported
by an Australian Research Council Fellowship.
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