American Bison - Buffalo Field Campaign

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9.2.2 Herd-level population and genetic management For many conservation herds, the most frequent and contentious decisions will concern herd level management, especially population control. Key decisions address how many animals to maintain, which ones to remove, and how often to remove them, when to add animals, and where to source them. This section provides advice for active population management at the herd level—guidelines for establishing a new herd, maintaining the size of an existing herd, reducing the size of a herd that has become much too large, and how to deal with known genetic issues. 9.2.2.1 Soft release procedures Bison may need to be moved to supplement an existing herd, or to establish a new herd. In such cases, the use of a “soft” release process should be considered in virtually all cases. Soft releases typically involve placing animals in a (usually large) holding facility prior to full release. Holding bison in a large pen may increase their tendency to remain in the area of release and establish some degree of site fidelity. American Prairie Foundation, for example, held bison for one month in a large corral prior to release on the American Prairie Reserve in Montana. An additional benefit of a soft release procedure is the effective quarantine and associated ability to monitor and more easily re-capture animals if any health issues become apparent. 9.2.3 Establishing a new herd Establishing and maintaining related, isolated or semi-isolated herds (i.e., parental and one or more satellite herds) is critical to long-term species conservation in that multiple herds act to increase effective population size (N e ) and reduce the total loss of genetic variation over time (Lande and Barrowclough 1987). Furthermore, the maintenance of a unique genetic population in several small herds reduces the probability of accidental extinction, such as from a natural catastrophe by disease, and increases the opportunity for local adaptation (Franklin 1980; Lacy 1987). In theory, and under experimental conditions, several small groups (e.g., N e about 50) may preserve more genetic diversity than a single herd with as many individuals as the smaller herds combined (Margan et al. 1998). Genetic drift within each related herd can be countered by the occasional movement of individuals between related herds (Mills and Allendorf 1996). Therefore, several moderately sized herds (i.e., more than 300 and fewer than 1,000 animals) of the same genetic stock can, if managed properly, act as a large metapopulation with an effective population size sufficient to impede genetic erosion (Lacy 1987). In this section, we articulate considerations for the establishment and maintenance of new bison herds from existing resources. 1. Source 88 American Bison: Status Survey and Conservation Guidelines 2010 Priority should be given to establishing satellite herds from extant conservation herds, within the respective original ranges for wood and plains bison, especially for those herds with unique genetic characteristics (Halbert 2003; Wilson and Strobeck 1999) and those which appear to be free of domestic cattle introgression (Ward et al. 1999; Halbert 2003; Halbert et al. 2005b). Beyond this, establishment of herds of mixed ancestry should be considered to maximise genetic diversity and the potential for adaptive response. Although bison are likely to be more readily available from herds subjected to artificial selection and some level of domestication, we strongly recommend acquiring bison from “wild” herds not subjected to these influences. 2. Number of animals Little specific information is available regarding appropriate foundation populations sizes. In general, a few (4-10) individuals should be sufficient to avoid very short-term inbreeding effects (Senner 1980). However, the loss of variation in such a small population will be substantial after the first few years (Nei et al. 1975) and additional bison should be imported over a period of several years to increase genetic variation. If the goal is to conserve or duplicate most of the genetic material in a source herd, many more animals are required. Shury et al. (2006) proposed a base of 200 “founder” animals to preserve most of the genetic variability in “re-established” wood bison herds. 3. Sex ratio The initial imported bison should consist of approximately 50% of each sex, and the herd should be maintained with a balanced sex ratio to reduce inbreeding and maximise effective population size. 4. Breeding strategy If a small number of bison are used to found a herd, and especially if additional bison are not brought into the new herd, breeding strategies to maximise the transfer of genetic diversity across generations should be considered (e.g., avoid excessive breeding by one or a few males). Appropriate genetic tools are available to accurately assign parentage in bison (Schnabel et al. 2000; Wilson et al. 2002), and these may be used to assist in captive breeding decisions by evaluating the breeding success of individual bulls and relatedness among calves. 5. Age composition and behaviour Bison are social animals and the importance of social structure within a herd is critical to overall herd health and survival (McHugh 1958). We recommend establishing a new herd with both adult and sub-adult individuals to prevent disintegration of social structure and behavioural anomalies (e.g., foraging behaviour; Ralphs and Provenza 1999).
6. Maintenance number and growth rate To minimise the loss of genetic variation and heterozygosity, and to maximise the probability of population survival, new herds should be allowed to grow as quickly as possible until the target herd size is attained (Nei et al. 1975). Bison herds can grow very quickly, doubling in size in as few as four years (see Chapter 6). Herds should then be maintained within an appropriate size range, which will likely be the maximum size possible within resource limits for herds with fewer than about 1,000 animals (Gross et al. 2006; Senner 1980). For small herds, fluctuations in population size can have a substantial negative impact on retention of genetic variation (Nei et al. 1975). Maintenance of population size is more important to population survival than is the founder population size and should, therefore, be given a high priority for small herds (Senner 1980). 7. Relationship between founders Select unrelated individuals as founders for a new herd. Use appropriate genetic tools when available to establish relatedness between bison (Schnabel et al. 2000; Wilson et al. 2002). 8. Genetic variation and heterozygosity Genetic evaluation should be carried out on the parental herd prior to establishment of a satellite herd, and repeated genetic evaluation of the satellite herd should be used to ensure that all the genetic variation from the parental herd are incorporated and maintained. 9. Disease In general, do not use diseased bison to establish a new herd. Immune suppression in diseased individuals may lead to infection and spread of other diseases; further compromising herd establishment and health. One notable exception is the intentional creation of disease-free satellite herds from a diseased parental herd. In such cases, use extra precautions to prevent the spread of disease from bison to other wildlife during the initial disease elimination phase. 10. Monitoring success Because it is expensive and time-consuming to establish bison herds, resources should be wisely invested to monitor bison herds and broader ecological effects of bison. Ideally, habitat characteristics should be monitored using a valid statistical process before bison are introduced. Herd composition, demographic parameters, and genetic structure, especially in the first few generations following herd establishment, should be monitored, along with ecosystem changes. Additional monitoring guidelines are provided below. Trans-boundary transportation of bison to establish a new herd can introduce many administrative and regulatory considerations (Chapter 8). After an extended period of planning and negotiation, wood bison were transported from Canada to Alaska in 2008. Personnel with the relevant agencies may be consulted for advice on undertaking such an enterprise. 9.2.4 Maintaining or manipulating existing herd size When a bison herd appears in need of intervention to restore or improve genetic health and population viability, the first and most important activity is to thoroughly evaluate the current condition of the herd to avoid premature, unnecessary, or even damaging management decisions. There are no simple cookbook instructions that can be applied to any bison herd. The following list of baseline evaluations will help ensure that decisions are well informed: 1. Determine the history of the herd to provide insight into current levels of genetic variation and population structure. Try to determine: Number and origin of herd founders; Number and origin of any bison introduced following herd foundation (transfers); Historic records on population size, especially with regard to substantial changes over time. 2. Evaluate current population parameters to establish baseline measurements for future comparison and to detect attributes that may lead to changes in social structure or genetic variation. Variables of interest include: Census population size Effective population size (N e ; will not be possible in all cases and requires knowledge of breeding structure) Rate and direction of population size changes (e.g., is the herd expanding or contracting) Sex ratio Age structure 3. Note any indications of inbreeding within the herd, such as: Unusual phenotypic characters within the herd, especially any that have recently appeared; Recent decrease in recruitment rates; High rates of morphologically abnormal or non-motile sperm among breeding-age bulls; Relatively low levels of heterozygosity as compared with previous measurements or other bison herds of similar size and history (e.g., Halbert 2003; Wilson and Strobeck 1999). 4. Assess potential health problems in the herd, including: Presence of transmissible diseases, especially those which may influence population dynamics (e.g., BTB, brucellosis, MCF); Presence of disease agents in livestock species on nearby (especially adjacent) properties (e.g., cattle with JD, sheep carrying MCF). American Bison: Status Survey and Conservation Guidelines 2010 89
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American Bison Status Survey and Co
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American Bison Status Survey and Co
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Table of Contents Acknowledgements
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6.3 Demographics ..................
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9.6 Active Management: Handling, He
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This manuscript is the product of m
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ABS American Bison Society ABSG Ame
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The publication of this IUCN Americ
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and foothills. Bison have a profoun
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Chapter 1 Introduction: The Context
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composition and function, as well a
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Chapter 2 History of Bison in North
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Figure 2.1 Original ranges of plain
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Charles Alloway (Manitoba), Charles
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nomadic “Plains Indian Culture”
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Chapter 3 Taxonomy and Nomenclature
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demonstrate that Bison and Bos were
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from their original habitat near th
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Chapter 4 Genetics As a science, po
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Selection for diversity in one syst
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cross, however, the latter is more
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the conservation of the wild specie
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Chapter 5 Reportable or Notifiable
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one) followed by its widespread dis
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cattle at similar levels to S19 (Ch
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long as 156 days post-infection. So
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and elk herds migrate across severa
Page 55 and 56: These concepts are being developed
Page 57 and 58: Chapter 6 General Biology, Ecology
Page 59 and 60: leave the herd prior to calving or
Page 61 and 62: historically dependent on a combina
Page 63 and 64: 6.2.1.2.1 Northern mixed grasslands
Page 65 and 66: woodland caribou (Rangifer tarandus
Page 67 and 68: season: Wolfe and Kimball (1989) re
Page 69 and 70: Table 6.4 Age-specific reproductive
Page 71 and 72: 6.3.4 Population growth rates The r
Page 73 and 74: Chapter 7 Numerical and Geographic
Page 75 and 76: Sixty-two plains bison and 11 wood
Page 77 and 78: Figure 7.4 Representation of plains
Page 79 and 80: Plate 7.3 Male plains bison sparrin
Page 81 and 82: Chapter 8 Legal Status, Policy Issu
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Page 85 and 86: Table 8.1 Current legal status of p
Page 87 and 88: Table 8.1 (continued) Country/ Stat
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Page 95 and 96: 8.5 Overcoming Obstacles to the Eco
Page 97 and 98: indigenous peoples’ land (Dudley
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Page 101 and 102: 8.5.5.3 Mexico Since the original r
Page 103 and 104: Chapter 9 Conservation Guidelines f
Page 105: animals are proportionately removed
Page 109 and 110: 4. Health and disease All attempts
Page 111 and 112: Table 9.4 Important considerations
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Page 115 and 116: may not have been validated. Testin
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Page 119 and 120: 2. Determine the required scope of
Page 121 and 122: Chapter 10 Guidelines for Ecologica
Page 123 and 124: • Creating education, awareness a
Page 125 and 126: 10.3 The “Ecosystem Approach” f
Page 127 and 128: anywhere without engaging stakehold
Page 129 and 130: Interventions (e.g., supplemental f
Page 131 and 132: Agabriel, J. and Petit, M. 1996. Qu
Page 133 and 134: Byerly, R.M., Cooper, J.R., Meltzer
Page 135 and 136: Dragon D.C. and Rennie, R.P. 1995.
Page 137 and 138: Gilpin, M.E. and Soulé, M.E. 1986.
Page 139 and 140: Joern, A. 2005. Disturbance by fire
Page 141 and 142: Matthews, S.B. 1991. An assessment
Page 143 and 144: Possingham, H.P., Davies, I., Noble
Page 145 and 146: Shaw, J.H. 1995. How many bison ori
Page 147 and 148: van Zyll de Jong, C.G. 1986. A Syst
Page 149 and 150: Appendix A North American conservat
Page 151 and 152: Plains bison (continued) State/Prov
Page 154: INTERNATIONAL UNION FOR CONSERVATIO
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