Desert Bighorn Sheep Restoration in Texas: Survival, Population Dynamics, and Habitat
Notice bibliographique
Résumé
Bighorn sheep (Ovis canadensis) once occupied mountain ranges from western Canada\nto northern Mexico in North America. The distribution and abundance of mountain\nsheep in North America have declined from >500,000 historically, to 185,000 in the\n1990s. In Texas, there were 1,000-1,500 desert bighorn (O. c. mexicana) living in 16\nmountains ranges within the Trans-Pecos region during the late 1800s. Declines\nresulted from a combination of factors including competition for forage with domestic\nlivestock, introduced diseases from domestic animals, unrestricted hunting, and\nrestriction of movements by net-wire fencing. By the mid-1940s, bighorn sheep\npopulations were estimated at 35 individuals, and by early 1960s the last Texas native\ndesert bighorn was extirpated. One successful approach to the conservation of large\nmammals has been their translocation into former habitats. While translocation\nstrategies have been successful for many species, translocations of large ungulates can\nbe expensive and time consuming, as well as logistically and politically challenging.\nBeginning in 1957, the Texas Game and Fish Commission brought desert bighorn from\nArizona to a breeding facility to initiate a restoration process. Over the next 4 decades,\na total of 146 desert bighorn were transplanted to Texas facilities from other states.\nThis study was initiated to fill gaps in the autecological knowledge of desert bighorn in\norder to inform management decisions and maximize the potential for long–term\nsuccess of translocated desert bighorn populations. The objectives of this study\nincluded: (1) analysis of survival and cause-specific mortality, (2) assess various\nstrategies to conduct translocations of desert bighorn in Texas using a system modeling\napproach, and (3) evaluation of potential desert bighorn distributions utilizing a\nprobability occurrence distribution model at a landscape scale within the Trans-Pecos\nregion of Texas. Results for the first objective, from the 172 collared individuals a total\nof 57 mortalities was recorded (25 M, 32 F). Causes of mortality were: 27\nundeterminable, 20 by mountain lion predation (Puma concolor), 5 were attributed to\ncontagious ecthyma (parapox orf virus), 1 poached in Mexico, 1 birth complication, 1\ninfection due to a broken jaw, 1 ingestion of toxic vegetation (cloakfern,\nAstrolepis sinuate), and 1 fell from a cliff. For the second objective, results indicated\nthat the number of years required for the population to reach carrying capacity (1) was\nreduced when proportionally more females than males were reintroduced, (2) was\nreduced slightly more by shorter than by longer time lags between the initial and the\nsecond reintroduction, although differences were negligible, and (3) was reduced when\na larger number of animals (representing a larger proportion of carrying capacity) was\nreintroduced. Results for objective 3 showed slope (49.74%) to have the greatest\nvariability explanation followed by elevation (21.26%). The model was able to explain\n95.73% of variability by using 4 variables. Distribution values for slope demonstrated\nselection values ranging from 0.09 to 314, having a median of 56.6 with a lower\nquartile of 38.2 and upper quartile of 76.3. Elevation values showed greater selection\nfor elevations between 1,200 m and 1,600 m having the median of 1,459 m. Elevation\nvalues ranged from 721 m to 2,024 m. In conclusion, reintroductions are increasingly\nused to re-establish populations of threatened species. However, many reintroduction\nattempts have been unsuccessful and the main reasons of failure are seldom\nunderstood. Monitoring should continue to provide the primary tool by which we learn\nabout the success or failure of conservation investments.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».