Ord’s Kangaroo Rat (Dipodomys ordii) Recovery Strategy in Canada

Although it is best to first help species recover in nature, it is sometimes impossible and too risky. A more controlled method and last possible resort in preserving a species is captive breeding, which is the breeding of species in captivity without threats in hopes of reintroducing the species.

There are acknowledged problems of captive breeding programs which include (1) establishing self-sufficient captive populations, (2) poor success in reintroductions, (3) high costs, (4) domestication, (5) preemption of other recovery techniques, (6) disease outbreaks, and (7) maintaining administrative continuity have all been significant (Snyder 1996). To minimize the problems mentioned, one should first see if it is possible to take an alternative means of conservation which will eliminate many of the problems all together. For example, if the alternative is to reduce the threats or translocation (then there would not be the problem of domestication. Synder (1996) argues captive breeding must not be done prematurely or employed before a careful field evaluation of costs and benefits of all other conservation alternatives. It should only be used when deemed essential for species survival, a last resort in species recovery and not a preventive or long-term solution because of the inevitable genetic changes that occur in captive environments. If captive breeding must be used, it should operate under carefully defined conditions of disease prevention and genetic and behavioral management. The 7 problems mentioned especially genetics, behavior, disease, administration and cost will be addressed and minimized as much as possible in the paper.

Justification for captive breeding

Ord’s kangaroo rat (Dipodomys ordii) is endemic to the Americas and only species of Dipodomys in Canada. In Canada, the species occurs in small parts of sand hills in southwestern Saskatchewan and southeastern Alberta as a disjunct population at the northernmost part of the species’ distribution. (COSEWIC) There are 32 recognized subspecies of Ord’s kangaroo rats (Williams et al. 1993). The Canadian population of Ord’s Kangaroo Rat exists in uncharacteristically cold and wet conditions and are the only kangaroo rats known to use torpor to conserve energy during winter.

Its occurrence and area of occupancy have declined in recent decades because its sandy habitats are declining due to encroachment of vegetation, human land management, and human land use. (COSEWIC) Under current rate of decline, it has been projected there will be no active dunes remaining in the Middle Sand Hills by 2014 which is representative of other areas within the species’ range in Canada. Besides the loss and degradation of natural habitat threats, severe seasonal fluctuation in population size puts the Canadian population at imminent risk of extinction. COSWEIC

As of 2006, Ord’s Kangaroo Rats are considered endangered provincially and by COSEWIC. Although recovery efforts are in place to reduce threats to them in the wild such as laws and protection of habitat by provinces, it is still at great risk of extinction because its low numbers. It is unlikely that translocations of animals from more southern

localities would be effective or appropriate because the Canadian population may be endemic. The recovery of the Ord’s Kangaroo Rat is considered technically and biologicallyFeasible (Day 1956; Egoscue 1970). A captive breeding program should be established to reduced the risk of the imminent extinction of this charismatic subspecies which already has some expirated populations.

An alternative is a more expensive captive survival program to help them survivor the winter can also be considered.

Goals and Timelines

The goal is 1) restore and maintain self-sustaining populations of Ord’s Kangaroo Rat within species current range and 2) prevent the subspecies from imminent extinction while habitat conservation programs for prairie dunes are under taken and 3) increase knowledge and understanding of its ecology, ecosystems, and threats.

This captive breeding is a 5 year program inclusive to collection, breeding, and reintroduction. Because of the rare biology of this species, its winter survivorship is less than 10% (Kenny 1989) which means it would be possible to boost its population significantly just by collecting a sizeable population before winter, keeping them in milder conditions, breeding them in captivity, and reintroducing them throughout the spring and summer.

Collection

The Canadian population of kangaroo rats occurs in two discrete areas which are fragmented (COSEWIC) See fig 1. It is best to collect from its whole range to achieve a more diverse and comprehensive sample. However, it is not neccessay to create two separate breeding populations because they function as a metapopulation due to the highly dispersed and patchy nature of habitat and because patch turnover rates are high (COSEWIC).

It is important to collect them randomly because any rats caught will have significantly higher fitness which means more of their genes will be passed on. To attain genetic diversity, traps should be set up far apart and capture rats indiscriminately. However, those with diseases or potential dieases are not included to minimize probability of disease outbreak.

Collection during the early winter when they have already bred and population is relatively high. Winter time collection minimizes the amount of time in captivity which reduces costs and probability of domestication. It also slightly reduces the resource competition for wild kangaroo rats which has the positive effect of increasing their survivorship. Only population estimates is during spring which between 545 and 1,040. For detrimental alleles, the survival probability depends strongly on the initial population size and is nearly independent on the carrying capacity; for mildly deleterious alleles, the survival probability is more dependent on the carrying capacity than on the initial population size Thévenon 2002. However, since population genetics of Ord’s kangaroo rats have not been studied (COSEWIC), we will use the rule of thumb a good found population which can minimize many genetic problems; thus, 10% of the population, an estimated 100 individuals, will be collected.

After some generations, the level of inbreeding is large Thévenon 2002. A mechanism to alleviate this is to have a small collection effort every year which can minimize the ill effects of captive breeding such as inbreeding by introducing new genetic diversity into the captive breeding population.

Breeding

Ord’s kangaroo rat is a very suitable candidate for captive breeding because it has a short generation time and has been shown to breed in captivity (Day 1956). Kangaroo rats breed whenever conditions are favourable (Beatley 1969; Gummer 1997a), aboveground

(Engstrom and Dowler 1981), and generally from early spring to early autumn (Kenny 1989, Gummer 1997a). Adult females in Canada may rise up to 4 litters per year with an average litter size of 3 (Gummer 1997a). Juvenile females attain sexual maturity at approximately 47 d and males become reproductive at approximately 79% of adult body mass and 61 d of age. The generation length for this population is < 1 year.

All species are subject to the loss of genetic diversity as successive generations are produced in captivity (Lande & Barrowclough, 1987; Lacy, 1994). The loss of rare alleles and increase in homozygosity may lead to a decrease in fitness (Ralls & Ballou, 1983). Captive breeding may also lead to domestication of wildlife due to unintentional selection. Heritable changes to morphology, behaviour and physiology have all been documented in captive wildlife, yet these adaptations to the captive environment are seldom beneficial in the wild (Frankham et al., 1986). These changes can occur in a few generations in spite of efforts to minimize such forces, because the intensity of unintentional selection can be very strong.

The breeding program hopes to maximize offspring production while maintaining genetic diversity. They will be bred based on several strategies in reduces the ill effects of cative breeding. We will rotate mating trhough the year starting with minizing kinship, random mating, choice as they are able to breed up to 4 times a year. However, we will only breed them 3 times a year and release a portion of species back into the wild to keep costs low. If gradual reintroduction is found not to be successful we will change our reintroduction tactics. If it is found to be successful and we can maintain or sustain the wild population, the captive breeding pogram will be phased out.

Captive populations of endangered species are managed to preserve genetic diversity and retain reproductive fitness. Minimizing kinship (MK) has been predicted to maximize the retention of gene diversity in pedigreed populations with unequal founder representation. MK was compared with maximum avoidance of inbreeding (MAI) and random choice of parents (RAND) using Drosophila melanogaster. Forty replicate populations of each treatment were initiated with unequal founder representation and managed for four generations. MK retained significantly more gene diversity and allelic diversity based on six microsatellite loci and seven allozyme loci than MAI or RAND. Reproductive fitness under both benign and competitive conditions did not differ significantly among treatments. Of the methods considered, MK is currently the best available for the genetic management of captive populations. (Montgomery )

Although mostly likely it is not necessary, practical, or financial effective to protect kangaroo rats from predators and other threats during breeding because increased survivorship should be enough to boost the population. Preventive measures such as fencing breeding ground can be taken if funding allows.

It is important to minimize inbreeding depression because juvenile survival is strongly decreased by inbreeding depression in various taxa (Ralls 1979). Domestication which is attained by some combination of genetic changes occurring over generations and behavioral changes triggered by recurring environmental events in captivity must also be minimized (Price 1984). Genetic changes on the development of domestic phenotype result from inbreeding, genetic drift, artificial selection, natural selection in captivity, and relaxed selection. Since the ability of domestic animals to survive in nature depends on the extent to which the gene pool has been altered, natural gene pools should be protected when breeding wild animals in captivity reestablishing free-living natural populations. With these considerations,

(5) facilities; Zoos: Balmford (1996) Current priorities for ex situ conservation stress the importance of large vertebrates. We show that this hampers the efficient use of resources because such species are less likely to breed will in captivity than smaller-bodied taxa and, despite longer generation lengths, are more costly to maintain in long-term breeding programs. Moreover, although reintroduction to the wild frees zoo space for other species and is the ultimate aim of captive breeding, zoos show no tendency to target species for which continued habitat availability makes reintroduction a realistic prospect. We suggest that zoos adopt selection criteria that reflect the economic and biological realities of captive breeding and reintroduction if they are to maximize their contribution to species conservation, and we present data on the preferences of zoo visitors indicating that doing so need not adversely affect zoo attendance.

When an captive surrounding there is likely to be a change in the availability and/or accessibility of shelter, space, food and water, and by changes in predation and the social environment.price1984

Size: Black-footed ferrets born to reintroduced individuals quickly returned to their pre-captive size suggesting that a diminutive morphology ex situ did not have a genetic basis. The authors hypothesise that small cage size and environmental homogeneity inhibit the mechanical stimuli necessary for long bone development. These findings have ramifications for ex situ managers who need to create artificial captive settings that promote natural physical development. In the absence of such an environment, 'unnatural' morphologies can result that may contribute to poor fitness or perhaps even domestication.

Prevent dieases and macroparasites such as botfly larvae; Gummer et al. 1997)

Kangaroo rats are adapted to hot and dry desert environments (MacMillen 1983, French 1993, Tracy and Walsberg 2002). Their nocturnal and fossorial nature facilitates heat avoidance and water conservation (Mullen 1971). Kangaroo rats can survive without exogenous water: their metabolic requirements met by eating seeds (Schmidt- Nielsen 1964, MacMillen and Hinds 1983). They select seeds with the highest water content in feeding tests (Frank 1988), and seeds cached in burrows undergo hygroscopic uptake of water (Reichman et al. 1986, Nagy and Gruchacz 1994). Kangaroo rat nasal passages are

structured so that moisture condenses by counter- current heat exchange, minimizing water loss (Jackson and Schmidt-Nielsen 1964, Schmidt-Nielsen et al. 1970, Collins et al. 1971).

Canadian Ord’s kangaroo rats use daily torpor to conserve energy during winter (Gummer 1997a, Gummer and Robertson 2003c, Gummer 2005). Individual kangaroo rats carrying or implanted with temperature data-loggers used torpor exclusively during the winter when the ground was snow covered (Gummer 1997a, Gummer and Robertson 2003c, Gummer 2005). Torpor was used primarily during daylight hours, with bouts extending up to 17 h and body temperatures falling to 13.5 ºC. Animals aroused from torpor during early evening and presumably fed from underground food caches during the night. Individuals generally did not emerge from burrows if there was snow on the ground. Kangaroo rats entered torpor on up to 70 d per winter (Gummer 2005), though some individuals did not exhibit torpor during mild winters (Gummer 2005). The Canadian population of Ord’s kangaroo rats is the only population of the genus known to use torpor in the wild. Laboratory studies of congeners reveal a drastic mass loss and death within several days if they are forced into torpor through starvation and exposure to low temperatures (Dawson 1955, Carpenter 1966, Yousef and Dill 1971, Breyen et al. 1973, MacMillen 1983). Likewise, there are reports of captures and observations of Ord’s kangaroo rats aboveground in southern localities throughout the year (Reynolds 1958, Kenagy 1973, O’Farrell 1974, Nagy and Gruchacz 1994), even when air temperature approaches –19 ºC (Kenagy 1973, O’Farrell 1974) and there is up to 40% snow cover (Mullen 1971, Kenagy 1973, O’Farrell 1974).

(6) methods and potential for reintroduction;

Indeed Snyder et al. (1996) pointed outthat very few reintroduction programmes succeeded(11% for largely vertebrates at this time).

One of the key factors determining the success of reintroduction programs is the number of individuals released (Griffith et al. 1989; Veltman et al. 1996; Wolf et al. 1998). As a consequence, the guidelines of the World Conservation Union (IUCN) for translocations in general (IUCN 1987) and for reintroductions in particular (IUCN 1998) specifically call for the use of models "to specify the optimal number … of individuals to be released … to promote establishment of a viable population."

Several surveys of success rates for reintroduction programs (largely for mammals and birds) have been carried out (Griffith et al. 1989; Wolf et al. 1996; Wolf et al. 1998; Fischer & Lindenmayer 2000). All indicate that success rates are poor (<50%; Griffith et al. 1989; Beck et al. 1994) and search for factors that correlate with (and potentially cause) reintroduction success. These surveys suggest that major factors influencing success include the number of individuals released and the number of release attempts (Griffith et al. 1989; Veltman et al. 1996; Wolf et al. 1998).

and (7) an exit strategy (when and how you will know if the program is working or not, and what you will do then). You can (and should) make relevant assumptions (e.g., available space, resources for genetic analysis, public or political interest, etc.), but your program should also be realistic in terms of facilities, logistics, cost, etc.

In addition, captive-reared animals must be conditioned to live in nature prior to their release.price1984

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