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Rodriguez‐Cordero AL, Balaguera‐Reina SA, Gross BA, Munn M, Densmore LD. Assessing abundance-suitability models to prioritize conservation areas for the dwarf caimans in South America. Ecol Evol 2024; 14:e70235. [PMID: 39219570 PMCID: PMC11362219 DOI: 10.1002/ece3.70235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2024] [Accepted: 08/14/2024] [Indexed: 09/04/2024] Open
Abstract
Species-environment relationships have been extensively explored through species distribution models (SDM) and species abundance models (SAM), which have become key components to understand the spatial ecology and population dynamics directed at biodiversity conservation. Nonetheless, within the internal structure of species' ranges, habitat suitability and species abundance do not always show similar patterns, and using information derived from either SDM or SAM could be incomplete and mislead conservation efforts. We gauged support for the abundance-suitability relationship and used the combined information to prioritize the conservation of South American dwarf caimans (Paleosuchus palpebrosus and P. trigonatus). We used 7 environmental predictor sets (surface water, human impact, topography, precipitation, temperature, dynamic habitat indices, soil temperature), 2 regressions methods (Generalized Linear Models-GLM, Generalized Additive Models-GAM), and 4 parametric distributions (Binomial, Poisson, Negative binomial, Gamma) to develop distribution and abundance models. We used the best predictive models to define four categories (low, medium, high, very high) to plan species conservation. The best distribution and abundance models for both Paleosuchus species included a combination of all predictor sets, except for the best abundance model for P. trigonatus which incorporated only temperature, precipitation, surface water, human impact, and topography. We found non-consistent and low explanatory power of environmental suitability to predict abundance which aligns with previous studies relating SDM-SAM. We extracted the most relevant information from each optimal SDM and SAM and created a consensus model (2,790,583 km2) that we categorized as low (39.6%), medium (42.7%), high (14.9%), and very high (2.8%) conservation priorities. We identified 279,338 km2 where conservation must be critically prioritized and only 29% of these areas are under protection. We concluded that optimal models from correlative methods can be used to provide a systematic prioritization scheme to promote conservation and as surrogates to generate insights for quantifying ecological patterns.
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Affiliation(s)
| | | | - Brandon A. Gross
- Department of Biological SciencesTexas Tech UniversityLubbockTexasUSA
| | - Margaret Munn
- Department of Biological SciencesTexas Tech UniversityLubbockTexasUSA
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Dhami B, Maraseni T, Thapa K, K. C. N, Subedi S, Gautam S, Ayer S, Bayne E. Gharial ( Gavialis gangeticus) conservation in Bardia National Park, Nepal: Assessing population structure and habitat characteristics along the river channel amidst infrastructure development. Ecol Evol 2023; 13:e10661. [PMID: 38020685 PMCID: PMC10630156 DOI: 10.1002/ece3.10661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 10/05/2023] [Accepted: 10/09/2023] [Indexed: 12/01/2023] Open
Abstract
Nepal initiated numerous hydropower and irrigation-related infrastructure projects to enhance and promote green energy, water security, and agricultural productivity. However, these projects may pose risks to natural habitats and the well-being of aquatic fauna, leading to significant effects on delicate ecosystems. To understand these potential impacts, it is crucial to gather reliable baseline data on the population status and habitat characteristics of species. This study specifically focuses on Gharials (Gavialis gangeticus), a critically endangered species. We recorded data on pre-determined habitat variables at stations spaced 500 m apart along the two major river streams of Bardia National Park, as well as at locations where Gharials were sighted between February and March 2023. We used binary logistic regression with a logit link function to investigate the habitat characteristics related to the occurrence of Gharials. The presence/absence of Gharials at sampling points served as the dependent variable, while 10 other predetermined variables (ecological variables and disturbance variables) served as independent variables. Our study recorded 23 Gharials, comprising 14 adults, six sub-adults, and three juveniles, with a sex ratio of 55.56 males per 100 females. Most individuals (83%) were found basking. Among the 10 habitat predictors, three variables (mid-river depth, river width, and water temperature) were significantly correlated (p < .05) with the probability of Gharial occurrence. The model shows that Gharial detection probability increases with greater mid-river depth and width and lower water temperature. This study establishes a population baseline for Gharials within the river system before the construction of large infrastructure projects, such as dams and irrigation canals. It also recommends continuous monitoring of Gharial populations after water release and/or diversion to evaluate the impact of large infrastructure projects on the population and their associated habitat characteristics. This will help enable more informed and targeted conservation efforts.
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Affiliation(s)
- Bijaya Dhami
- Department of Biological SciencesUniversity of AlbertaEdmontonAlbertaCanada
| | - Tek Maraseni
- University of Southern QueenslandToowoombaQueenslandAustralia
| | | | | | - Sanskar Subedi
- Institute of Forestry Pokhara CampusTribhuvan UniversityPokharaNepal
| | - Shreejan Gautam
- Institute of Forestry Pokhara CampusTribhuvan UniversityPokharaNepal
| | - Santosh Ayer
- College of Natural Resource Management (CNRM)Agriculture and Forestry UniversityKatariNepal
| | - Erin Bayne
- Department of Biological SciencesUniversity of AlbertaEdmontonAlbertaCanada
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Lawson AJ, Jodice PGR, Rainwater TR, Dunham KD, Hart M, Butfiloski JW, Wilkinson PM, McFadden KW, Moore CT. Hidden in plain sight: Integrated population models to resolve partially observable latent population structure. Ecosphere 2022. [DOI: 10.1002/ecs2.4321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Abigail J. Lawson
- Department of Forestry and Environmental Conservation Clemson University Clemson South Carolina USA
| | - Patrick G. R. Jodice
- U.S. Geological Survey, South Carolina Cooperative Fish and Wildlife Research Unit Clemson University Clemson South Carolina USA
| | - Thomas R. Rainwater
- Department of Forestry and Environmental Conservation Clemson University Clemson South Carolina USA
- Baruch Institute of Coastal Ecology and Forest Science Clemson University Georgetown South Carolina USA
- Tom Yawkey Wildlife Center Georgetown South Carolina USA
| | - Kylee D. Dunham
- U.S. Geological Survey, Eastern Ecological Science Center Laurel Maryland USA
| | - Morgan Hart
- South Carolina Department of Natural Resources Columbia South Carolina USA
| | | | | | - K. W. McFadden
- U.S. Geological Survey, South Carolina Cooperative Fish and Wildlife Research Unit Clemson University Clemson South Carolina USA
| | - Clinton T. Moore
- U.S. Geological Survey, Georgia Cooperative Fish and Wildlife Research Unit, Warnell School of Forestry and Natural Resources University of Georgia Athens Georgia USA
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Utkarsha Manish Chavan, Borkar MR. Population trends of Mugger Crocodile and human-crocodile interactions along the Savitri River at Mahad, Maharashtra, India. JOURNAL OF THREATENED TAXA 2022. [DOI: 10.11609/jott.7934.14.11.22118-22132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
In this paper, we report monitoring of a resident population of Mugger Crocodile Crocodylus palustris (Lesson, 1831) along a stretch of 3.5 km of the river Savitri on the outskirts of Mahad town of Raigad District in Maharashtra, on monthly basis from 2014 to 2021. This river is increasingly becoming a sink of anthropogenic wastes emerging from adjacent settlements impacting its habitat value, and puts the reptile side by side with humans and human-wastes that could be a cause of rising incidents of crocodile mortality in the recent times here, as also reported from elsewhere. Savitri River has been a fishing ground for local indigenous communities, who also use the river bank for washing clothes and utensils, and for swimming. Such proximity between people and crocodiles creates a potential for negative interaction. This long term study monitored the Mugger population trends for the last eight years at four transect stretches along the river. Counts are suggestive of a healthy viable population of Mugger in this river currently, but a future conflict situation cannot be ruled out. Being generalist feeders, Muggers can sustain themselves on fish, and scavenge on dumped carrion and other anthropogenic organic wastes. With the exception of a few sporadic incidents of aggression by the Muggers at this location, no human casualties have been reported thus far, however, this does not rule out fatal reciprocal interactions in future and hence a few practical mitigation measures have been suggested.
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Yadav RK, Lamichhane S, Thanet DR, Rayamajhi T, Bhattarai S, Bashyal A, Lamichhane BR. Gharial ( Gavialis gangeticus, Gmelin, 1789) abundance in the Rapti River, Chitwan National Park, Nepal. Ecol Evol 2022; 12:e9425. [PMID: 36267686 PMCID: PMC9579734 DOI: 10.1002/ece3.9425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 09/16/2022] [Accepted: 09/26/2022] [Indexed: 11/17/2022] Open
Abstract
Gharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers is low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nepal. The Rapti River, running across the CNP, was divided into 18 segments, each measuring ~4 km, and gharials were counted directly with three replicates. Gharial count data were analyzed using an N-mixture model (negative binomial) and the overall occupancy of gharials was estimated using a single season occupancy model. Covariate effects were also investigated on gharial abundance. Our findings revealed that the Rapti River is home to 150 gharials (119-181), with a mean abundance of 8.3 (SD = 3.45) across each segment. The presence of humans and square of Rapti River depth were the significant covariates that had a negative and positive impact on gharial abundance, respectively. Similarly, the number of sandbank present influenced the detection probability of gharials. Our study shows that gharial population estimation can be improved using the N-mixture model. The overall gharial occupancy estimated using single season occupancy model was 0.84 (SD = 0.08), with a detection probability of 0.37 (SD = 0.02). The management authority should concentrate on segments to minimize human disturbance (e.g., fishing, washing clothes, extraction of riverbed materials). If the gharial population in this river declines, their population in central Nepal will be threatened. Hence, we suggest designating the Rapti River section that passes across the CNP as a "no extraction zone."
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Affiliation(s)
- Ramesh Kumar Yadav
- Department of National Parks and Wildlife ConservationKanchenjunga Conservation AreaTapethokNepal
| | - Saneer Lamichhane
- National Trust for Nature ConservationRatnanagar, ChitwanNepal
- Birat Environment ServiceBiratnagarNepal
- Nepal Conservation and Research CenterRatnanagarChitwanNepal
- Present address:
University of FloridaGainesvilleFloridaUSA
| | | | - Trishna Rayamajhi
- Department of Natural Resources and the EnvironmentCornell UniversityIthacaNew YorkUSA
| | - Santosh Bhattarai
- Nepal Conservation and Research CenterRatnanagarChitwanNepal
- Present address:
Federation UniversityChurchillVictoriaAustralia
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Lemos Barão-Nóbrega JA, González-Jaurégui M, Jehle R. N-mixture models provide informative crocodile ( Crocodylus moreletii) abundance estimates in dynamic environments. PeerJ 2022; 10:e12906. [PMID: 35341055 PMCID: PMC8944345 DOI: 10.7717/peerj.12906] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 01/17/2022] [Indexed: 01/11/2023] Open
Abstract
Estimates of animal abundance provide essential information for population ecological studies. However, the recording of individuals in the field can be challenging, and accurate estimates require analytical techniques which account for imperfect detection. Here, we quantify local abundances and overall population size of Morelet's crocodiles (Crocodylus moreletii) in the region of Calakmul (Campeche, Mexico), comparing traditional approaches for crocodylians (Minimum Population Size-MPS; King's Visible Fraction Method-VFM) with binomial N-mixture models based on Poisson, zero-inflated Poisson (ZIP) and negative binomial (NB) distributions. A total of 191 nocturnal spotlight surveys were conducted across 40 representative locations (hydrologically highly dynamic aquatic sites locally known as aguadas) over a period of 3 years (2017-2019). Local abundance estimates revealed a median of 1 both through MPS (min-max: 0-89; first and third quartiles, Q1-Q3: 0-7) and VFM (0-112; Q1-Q3: 0-9) non-hatchling C. moreletii for each aguada, respectively. The ZIP based N-mixture approach shown overall superior confidence over Poisson and NB, and revealed a median of 6 ± 3 individuals (min = 0; max = 120 ± 18; Q1 = 0; Q3 = 18 ± 4) jointly with higher detectabilities in drying aguadas with low and intermediate vegetation cover. Extrapolating these inferences across all waterbodies in the study area yielded an estimated ~10,000 (7,000-11,000) C. moreletii present, highlighting Calakmul as an important region for this species. Because covariates enable insights into population responses to local environmental conditions, N-mixture models applied to spotlight count data result in particularly insightful estimates of crocodylian detection and abundance.
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Affiliation(s)
- José António Lemos Barão-Nóbrega
- Operation Wallacea, Spilsby, Lincolnshire, United Kingdom,School of Science, Engineering and Environment, University of Salford, Salford, Greater Manchester, United Kingdom
| | - Mauricio González-Jaurégui
- Universidad Autónoma de Campeche, Centro de Estudios de Desarrollo Sustentable y Aprovechamiento de la Vida Silvestre, Campeche, Campeche, Mexico
| | - Robert Jehle
- School of Science, Engineering and Environment, University of Salford, Salford, Greater Manchester, United Kingdom
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Utete B. A review of the conservation status of the Nile crocodile (Crocodylus niloticus Laurenti, 1768) in aquatic systems of Zimbabwe. Glob Ecol Conserv 2021. [DOI: 10.1016/j.gecco.2021.e01743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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Balaguera‐Reina SA, Vargas‐Castillo A, Densmore LD. Population ecology of the spectacled caiman (
Caiman crocodilus
) in the Apaporis River middle basin. Ecosphere 2021. [DOI: 10.1002/ecs2.3532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Sergio A. Balaguera‐Reina
- Programa de Biología Ambiental Facultad de Ciencias Naturales y Matemáticas Universidad de Ibagué Carrera 22 Calle 67 Ibague730001Colombia
- Department of Biological Sciences Texas Tech University Lubbock Texas79409USA
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Than KZ, Strine CT, Sritongchuay T, Zaw Z, Hughes AC. Estimating population status and site occupancy of saltwater crocodiles Crocodylus porosus in the Ayeyarwady delta, Myanmar: Inferences from spatial modeling techniques. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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10
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Kaminski DJ, Harms TM, Coffey JM. Using spotlight observations to predict resource selection and abundance for white‐tailed deer. J Wildl Manage 2019. [DOI: 10.1002/jwmg.21729] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Dan J. Kaminski
- Iowa Department of Natural ResourcesBoone Research Station, 1436 255th StreetBoone IA 50036 USA
| | - Tyler M. Harms
- Iowa Department of Natural ResourcesBoone Research Station, 1436 255th StreetBoone IA 50036 USA
| | - Jim M. Coffey
- Iowa Department of Natural ResourcesChariton Research Station, 24570 US Highway 34, Chariton IA 50049 USA
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