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Cited by 24Wildlife Ecology and ConservationPrimate Behavior and EcologyWildlife Conservation and Criminology Analyses

Field surveys for the Endangered pygmy hippopotamus Choeropsis liberiensis in Sapo National Park, Liberia

Open access
Collen, Ben, Howard, Robert, Konie, John, Daniel, Olivia, Rist, Janna·2011·Oryx
DOI 10.1017/s0030605310001444
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Abstract

Conservation of a threatened species is reliant upon good quality monitoring information to provide population estimates and trends to inform management practices. Surveying to establish such data can be costly and difficult, particularly for cryptic species in forest habitats. We therefore used remotely triggered cameras to survey for the presence of the pygmy hippopotamus Choeropsis liberiensis in Sapo National Park in Liberia. In 1,247 trap days we obtained seven camera-trap photographs, the first photographic records of the species in Liberia. Habitat destruction, principally from illegal gold mining, is the greatest threat to the persistence of the pygmy hippopotamus within the Park. A range-wide survey of the pygmy hippopotamus is required to establish a robust baseline from which future conservation efforts can be developed. Understanding how this species is able to cope with the effects of habitat fragmentation across its range, and controlling commercial hunting, will dictate how it is able to survive the ongoing pressures of land conversion in West Africa.

AI snapshot

Written from the paper’s full text.

TL;DR

A camera-trap survey in Sapo National Park, Liberia, produced the first photographic records of the Endangered pygmy hippopotamus in Liberia: seven camera-trap events over 1,247 trap days, all at one station. The authors conclude that habitat destruction, principally from illegal gold mining, is the greatest threat within the Park and that a range-wide survey is needed to establish a robust baseline.

Key findings

  • In 1,247 camera trap days, the survey obtained seven camera-trap photographs/events of pygmy hippopotamuses, the first photographic records of the species in Liberia. All records came from the same camera trap station, in seasonally inundated primary forest on the inside of a river meander, just inside the 2005 boundary extension of Sapo National Park.
  • Footprint and scat signs of the species were recorded in two further locations, both in similar habitat.
  • Lack of photographs from other cameras could be because those cameras were located in different habitat, specifically higher altitude and secondary forest.
  • The number of trap events was not sufficient to estimate absolute density; the authors state that a more targeted survey is required, and that habitat destruction, principally from illegal gold mining, is the greatest threat to the species’ persistence within the Park.

Methods

  • Camera-trap survey using infrared heat- and motion-triggered digital cameras from 24 January to 23 March 2008 in Zone 1 of Sapo National Park, Liberia, designed to detect wide-ranging and cryptic species.
  • Thirty-two cameras were spaced at 2-km intervals and set 40 cm from the ground; each grid-square centre was located by GPS, and cameras were secured in an optimal location (e.g. a recently used animal trail) within a 100-m radius of the centre.
  • A total of 1,247 camera trap days were achieved; records were assessed as camera-trap events, with sign surveys also noting footprints and scats.

Limitations

  • The paper states that the number of trap events was not sufficient to employ methods for estimating absolute density without individual recognition, and that a more targeted survey, rather than the general scheme used, is required.
  • The paper states that lack of photographs from other cameras could be because other cameras were located in different habitat (higher altitude, secondary forest).
  • Evident from the text: only one camera trap station yielded photographic records, so the survey provides limited spatial inference and no population estimate or trend; the authors also note that confirmation of home range sizes using radio telemetry would help guide optimal grid size for measuring change in occupancy.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1017/s0030605310001444

Cites

11 of 11 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

4 of 17 cited sources checked · 2 supported · 0 flagged · accuracy not yet measured

  • Findingown data

    Footprint and scat signs of pygmy hippopotamus were recorded in two further locations, both in similar habitat.

    “Footprint and scat signs of the species were recorded in two further locations, both of which were in similar habitat.”
    Quote in the paperNot a substantial claim
  • Premisecitation

    The most acute period of range decline (inferred from habitat loss) for the pygmy hippopotamus has been over the past 3 decades.

    “the most acute period of range decline (inferred from habitat loss) has been over the past 3 decades (Lewison & Oliver, 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Lewison & Oliver, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Premisecitation

    The most recent population estimate for the pygmy hippopotamus was c. 3,000 in the early 1990s.

    “the most recent population estimate, of c. 3,000, was made in the early 1990s (Lewison & Oliver, 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Lewison & Oliver, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Study design and conductown data

    The number of trap events in this study was not sufficient to employ methods to estimate absolute density without the need for individual recognition.

    “Although methods to estimate absolute density without the need for individual recognition continue to be developed (Rowcliffe et al., 2008) the number of trap events in this study were not sufficient to employ such methods.”
    Quote in the paperSubstantial claim
  • Premisecitation

    The pygmy hippopotamus is categorized as Endangered on the IUCN Red List.

    “The species is categorized as Endangered on the IUCN Red List”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Lewison & Oliver, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim. 12
  • May combine two claims. 8

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The forests of Liberia declined by 2.9% between 1986 and 2000, but rates were higher in Côte d'Ivoire.

    “The forests of Liberia declined by 2.9% between 1986 and 2000 (Christie et al., 2007) but rates were higher in Co ˆte d'Ivoire.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Christie et al., 2007 source

  • Classified as probably not a substantial claim.

    Premisecitation

    The pygmy hippopotamus is a candidate for priority conservation attention because of its threatened status, long independent evolutionary heritage, and ongoing threats.

    “Its threatened status, long independent evolutionary heritage, and ongoing threats make the pygmy hippopotamus a candidate for priority conservation attention (Isaac et al., 2007).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Isaac et al., 2007 source

      The Introduction and Discussion (pages unavailable) support prioritising mammals that combine extinction risk with substantial evolutionary distinctiveness. But the passages found for 'pygmy hippopotamus' and its scientific names do not identify this species as a priority or establish its threatened status, independent evolutionary heritage, or ongoing threats. (LLM, conf=0.79)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Camera-trap monitoring is rapidly gaining acceptance.

    “Camera-trap monitoring is rapidly gaining acceptance (Rowcliffe & Carbone, 2008)”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Rowcliffe & Carbone, 2008 source

  • May combine two claims.

    Premisecitation

    Transect methods using spoor and droppings must deal with differences in skill levels of those conducting the survey, and decay and defecation rates, all of which contribute to inaccuracy and increased variance in abundance estimates.

    “Transect methods using spoor and droppings must deal with differences in skill levels of those conducting the survey, and decay and defecation rates, all of which contribute to inaccuracy and increased variance in abundance estimates (Plumptre, 2000).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites Plumptre, 2000 source

      The Defaecation rates section says errors in deposition and decay rates should be included in estimates from indirect counts; the Decay rates section says variation in decay rates reduces the resolution of dung and nest counts. These passages support the concern about inaccurate or imprecise abundance estimates, but the passages found do not address differences in surveyors’ skill levels or specifically discuss spoor. Page numbers are not available in our copy. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    In 1,247 camera trap days, seven camera-trap photographs of pygmy hippopotamus were obtained, the first photographic records of the species in Liberia.

    “In 1,247 trap days we obtained seven camera-trap photographs, the first photographic records of the species in Liberia.”
    • Also stated in: § Abstract · plain
      “Seven camera-trap events provided photographic records of pygmy hippopotamuses (Plate 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    All seven camera-trap records of pygmy hippopotamus were from the same camera trap station, in seasonally inundated primary forest on the inside of a river meander, just inside the 2005 boundary extension of Sapo National Park.

    “All records were from the same camera trap station, in seasonally inundated primary forest on the inside of a river meander, just inside the 2005 boundary extension the Park.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Habitat destruction, principally from illegal gold mining, is the greatest threat to the persistence of the pygmy hippopotamus within Sapo National Park.

    “Habitat destruction, principally from illegal gold mining, is the greatest threat to the persistence of the pygmy hippopotamus within the Park.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The presence of miners in Sapo National Park had resulted in habitat destruction, pollution of water courses, and commercial and subsistence hunting by the miners and their families.

  • May combine two claims.

    Premisecitation

    The largest fragment of the pygmy hippopotamus's former range is the contiguous Upper Guinea forest in Liberia and Côte d'Ivoire, and this area probably harbours the majority of the remaining population.

    “The largest fragment of the species' former range is the contiguous Upper Guinea forest in Liberia and Co ˆte d'Ivoire and this area probably harbours the majority of the remaining population (IUCN Hippo Specialist Group, 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites IUCN Hippo Specialist Group, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Premisecitation

    Average home range for C. liberiensis is estimated to be 0.4-0.5 km2 for females and 1.5 km2 for males.

    “Average home range for C. liberiensis is estimated to be 0.4-0.5 km 2 for females and 1.5 km 2 for males (Roth et al., 2004).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Roth et al., 2004 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The Nigerian subpopulation of pygmy hippopotamus is thought to be extinct.

    “This map excludes the Nigerian subpopulation, which is thought to be extinct(Lewison & Oliver, 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Lewison & Oliver, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    If cells are smaller than average home range then the measure is a measure of intensity of habitat use.

    “If cells are smaller than average home range then the measure is a measure of intensity of habitat use (Royle & Nichols, 2003).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Royle & Nichols, 2003 source

  • May combine two claims.

    Premisecitation

    The main threats to the pygmy hippopotamus include habitat fragmentation, land conversion and hunting.

    “The main threats to the species include habitat fragmentation, land conversion and hunting (Roth et al., 2004).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Roth et al., 2004 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Lack of photographs from other cameras could be because other cameras were located in different habitat (higher altitude, secondary forest).

    “Lack of photographs from the other cameras could be because other cameras were located in different habitat (higher altitude, secondary forest).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Priorities for pygmy hippopotamus conservation include establishing a reliable method for assessing the sizes of the various populations, and monitoring the species in protected areas using census techniques.

    “Priorities for the conservation of the pygmy hippopotamus include establishing a reliable method for assessing the sizes of the various populations, and monitoring the species in protected areas using census techniques (Lewison & Oliver, 2008).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Lewison & Oliver, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Premisecitation

    Sapo National Park is a stronghold of the pygmy hippopotamus.

    “we carried out camera-trap monitoring in Sapo National Park (Fig. 1), a stronghold of the species (IUCN Hippo Specialist Group, 2008).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites IUCN Hippo Specialist Group, 2008

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Land conversion continues at a rapid pace, principally because of agricultural expansion, wood extraction and infrastructure development.

    “Land conversion continues at a rapid pace, principally because of agricultural expansion, wood extraction and infrastructure development (Norris et al., 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Norris et al., 2010 source

  • Classified as probably not a substantial claim.

    Premisecitation

    An ideal grid to track changes in occupancy would have cells with an area approximately equal to home range size, such that changes in the population would generate changes in the proportion of area occupied.

    “An ideal grid to track changes in occupancy would have cells with an area approximately equal to home range size, such that changes in the population would generate changes in the proportion of area occupied (MacKenzie et al., 2002).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites MacKenzie et al., 2002 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    New standardized camera-trap methods have been advocated for landscape-scale monitoring.

    “new standardized camera-trap methods have been advocated for landscape-scale monitoring (O'Brien et al., 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites O'Brien et al., 2010 source
18 of 18

  • The paper relies on this without support.

    Conservation of the pygmy hippopotamus is hampered by a lack of basic biological knowledge, including details of distribution, population trends and ecology.

    “Conservation of the pygmy hippopotamus is hampered by a lack of basic biological knowledge, including details of distribution, population trends and ecology.”

  • The paper relies on this without support.

    Observational records of the pygmy hippopotamus are scant because of its cryptic nature.

    “Observational records of the species are scant because of its cryptic nature”

  • The paper relies on this without support.

    During the Liberian civil wars (1989-1996 and 1999-2003) many hundreds of hunters and gold miners inhabited Sapo National Park.

    “During the Liberian civil wars (1989-1996 and 1999-2003) many hundreds of hunters and gold miners inhabited the Park.”

  • The paper relies on this without support.

    The presence of miners in Sapo National Park had resulted in habitat destruction, pollution of water courses, and commercial and subsistence hunting by the miners and their families.

    “Their presence had resulted in habitat destruction, pollution of water courses, and commercial and subsistence hunting by the miners and their families.”

  • The paper relies on this without support.

    Conservation of a threatened species is reliant upon good quality monitoring information to provide population estimates and trends to inform management practices.

    “Conservation of a threatened species is reliant upon good quality monitoring information to provide population estimates and trends to inform management practices.”

  • The paper relies on this without support.

    Surveying to establish such data can be costly and difficult, particularly for cryptic species in forest habitats.

    “Surveying to establish such data can be costly and difficult, particularly for cryptic species in forest habitats.”

  • The paper relies on this without support.

    Cost effective and accurate monitoring of rare and cryptic species is problematic.

    “Cost effective and accurate monitoring of rare and cryptic species is problematic.”
7 of 7

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Most recent records of the pygmy hippopotamus have come from within protected areas.

    “Although most recent records have come from within protected areas (Collen et al., ; Mallon et al., ) this may represent sampling bias, as such sites are often targeted for biodiversity surveys.”

    From A mix of community-based conservation and protected forests is needed for the survival of the Endangered pygmy hippopotamus<i>Choeropsis liberiensis</i> (2017) · cites this paper as Collen et al., 2011

    The Abstract and survey account (page not specified in our copy) report recent pygmy hippopotamus photographs and signs from Sapo National Park, a protected area. The paper does not compare records across protected and unprotected areas, so it does not establish that most recent records came from protected areas. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

  • Other recent confirmed records of C. liberiensis are from Gola National Forest in the west, from the Wonegizi National Forest in the north, on the border with Guinea, and in Sapo National Park in the southeast.

    “Other recent confirmed records are from Gola National Forest in the west, from the Wonegizi National Forest in the north, on the border with Guinea, and in Sapo National Park in the southeast (Collen et al. 2011).”

    From Choeropsis liberiensis (Artiodactyla: Hippopotamidae) (2019) · cites this paper as Collen et al. 2011

    The Abstract reports seven camera-trap photographs confirming C. liberiensis in Sapo National Park, Liberia. Our copy does not report confirmed records from Gola National Forest or Wonegizi National Forest, so the citation supports only the Sapo portion of the sentence. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Camera trap photos of wild C. liberiensis repeatedly show the animals as subjectively thinner than their captive counterparts.

    “Camera trap photos of wild C. liberiensis repeatedly show the animals as subjectively thinner than their captive counterparts (Hentschel 1990;Collen et al. 2011;Eshuis 2011;Conway 2013).”

    From Choeropsis liberiensis (Artiodactyla: Hippopotamidae) (2019) · cites this paper as Collen et al. 2011

    The survey account (page not provided in our copy) reports seven camera-trap events that photographed wild pygmy hippopotamuses. It does not describe their apparent thinness or compare them with captive animals, so it supports the photographs but not the claimed comparison. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Observations of radio-collared animals and camera trap studies indicate that activity levels tend to peak from the late afternoon until around midnight and again in the early morning hours.

    “Observations of radio-collared animals (Bülow 1987;Hentschel 1990), as well as multiple camera trap studies throughout its range, indicate that activity levels tend to peak from the late afternoon until around midnight and again in the early morning hours (Collen et al. 2011;Eshuis 2011;van Heukelum 2011;Conway 2013).”

    From Choeropsis liberiensis (Artiodactyla: Hippopotamidae) (2019) · cites this paper as Collen et al. 2011

    The paper reports a camera-trap survey of pygmy hippopotamuses in Sapo National Park, so it supports identifying Collen et al. as a camera-trap study. The passage reporting seven photographic events does not give their times or describe peaks in activity from late afternoon to midnight or in the early morning (p. 35–37). (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • Pygmy hippopotami are known to inhabit the protected areas within their range.

    “There are 87 protected areas covering 30 669 km 2 that are partially or totally located inside the pygmy hippopotamus's range (UNEP-WCMC & IUCN 2021), and pygmy hippopotami are known to inhabit them (Roth et al. 2004, Collen et al. 2011, Garteh 2013, Conway et al. 2015, Bogui et al. 2016, Hillers et al. 2017, Ouattara et al. 2018).”

    From Forest loss during 2000–2019 in pygmy hippopotamus (<i>Choeropsis liberiensis</i>) habitats was driven by shifting agriculture (2024) · cites this paper as Collen et al. 2011

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. 2008, Hippo Specialist Group of the World Conservation Union
  2. Lewison, 2008, IUCN Red List of Threatened Species v. 2010.4

Cited by

Sorted by citations

Related

Authors
Collen, B., Howard, R., Konie, J., Daniel, O., & Rist, J.
Affiliations
  • Zoological Society of London (GB)
  • Fauna and Flora International (GB)
Corresponding author
Collen, Ben
ORCID
Venue
Oryx
Publisher
Cambridge University Press (CUP)
Published
2011-01
Volume
45
Issue
1
Pages
35-37
ISSN
  • 0030-6053 (ISSN-L)
  • 1365-3008
DOI
10.1017/s0030605310001444
OpenAlex
W2122033221
Cited by
24
References
11
Citations by year
2026: 1 · 2023: 2 · 2022: 1 · 2021: 1 · 2019: 3 · 2018: 1 · 2017: 2 · 2016: 2 · 2015: 2 · 2014: 3 · 2013: 2 · 2012: 2
FWCI
2.54
Type
journal article
Language
en
Open access
Licence
www.cambridge.org/core/terms (unspecified, 31 d)
Locations
  • Oryx (publishedVersion)
  • UCL Discovery (University College London) (submittedVersion)
Topics
  • Physical Sciences › Environmental Science › Ecology › Wildlife Ecology and Conservation
  • Social Sciences › Psychology › Social Psychology › Primate Behavior and Ecology
  • Physical Sciences › Environmental Science › Nature and Landscape Conservation › Wildlife Conservation and Criminology Analyses
Keywords
pygmy hippopotamus, Choeropsis liberiensis, camera trapping, species occurrence records, endangered species conservation, illegal gold mining, habitat loss, habitat fragmentation, commercial hunting, population monitoring, cryptic species

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