A Biophysical Inventory and Evaluation of the Lulu Island Bog Chapter 17: Mammals of the Lulu Island Bog by return to the inventory home page 17.1 Introduction Mammals, both large and small, were once abundant on Lulu Island. Historical records show that there was a resident population of deer on Lulu Island when the first settlers arrived (source?). Bears were also occasionally observed swimming to the island to forage (Kidd 1927). Other records show that there were elk on the island and other large mammals with large home ranges such as cougars and wolves (Ross 1979). Smaller mammals such as mink, beaver, muskrat, flying squirrels and rabbits are also recorded (Ross 1979, Klinkenberg and Klinkenberg 2001). However, as human settlement progressed, and agricultural and urban development increased on Lulu Island, habitat loss accelerated. Many large mammals such as bears, elk, cougars and wolves disappeared from the island. Today, other than our large wetlands, such as Sturgeon Banks, and the Iona spit, our island wildlife persists primarily in tiny fragments of habitat. Of these, the remnant Lulu Island Bog is one of the largest remaining natural area. The bog now plays a key role in maintaining residual wildlife populations on Lulu Island through provision of habitat and sanctuary in the midst of a sea of development, and its persistence is now critical to the survival of many animals species on the island. While most large mammals have disappeared from Lulu Island, deer and coyotes are still found, and occur in the bog. Deer (the Columbian Black-tailed Deer) are frequently sighted on the island, near or in the nature park and elsewhere. Deer tracks have been observed regularly in the bog as recently as /2003/2004/2005 by DND staff, Richmond Nature Park staff, and others (Griffith pers. com. 2004, Klinkenberg pers. comm. 2004, give name/source for DND anecdotal info?). Frequent signs of coyotes, such as scat and tracks, distinguish them as the largest natural predator in the study area. Foxes were observed in the nature park as recently as the 1970’s (source?) , but there are no recent records (have we checked with wildlife people to see if there are any road kills or other finds? What’s is the actual most recent record?). Beaver have a continuing presence on Lulu Island, with the presence of active beaver lodges at Garry Point and Green Slough, and in other locations proximal to the river (Klinkenberg and Klinkenberg 2001). Small mammals such as squirrels, moles, voles, mice and shrews generally have small enough home range requirements to permit the continued existence of populations on Lulu Island, and in the study area. Some species have not yet been confirmed in Richmond or on Lulu Island. Opossums, for example, are found in Delta, with fairly recent records, however this species is not yet reported for Richmond. 17.2 A fragmented bog Furthermore, the bog itself
is fragmented into three properties separated by roadways and drainage
ditches. One effect of fragmentation is its
influence on the movement of species between patches of habitat (Schtickzelle
and Baguette 2003). For small mammals such as rodents and insectivores,
roads, ditches and railway tracks can act as barriers or filters, preventing
or restricting movement between habitat patches, respectively (Witt
and Huntly 2001, McDonald and St. Clair 2004). Conversely, roads
may actually provide coyotes corridors for movement (Tigas, Van Vuren
and Sauvajot 2002). For species at
risk in this region, the implications of the bog as a refuge and as
a fragmented habitat could be of particular importance. The Lulu
Island Bog may be one of a small number of suitable habitats remaining
for such species. Based on habitats present in the bog, the above information,
and recent survey records, the small mammal inventory focused on three
species at risk extant in the lower mainland. The small mammal fauna of the Lulu Island Bog has never been thoroughly surveyed. Bell (1984) sampled briefly in the west property of the Richmond Nature Park (RNP west), and there are numerous recorded incidental sightings, photographs and captures of wildlife by park staff since the inception of the park. This inventory is the first to sample small mammals systematically across all three properties that comprise the remnant Lulu Island Bog. The small mammal inventory focused on rodents, insectivores, and hares. 17.3 Species at Risk The regional Species at Risk Biologist, Ross Vennesland (MOE), and Federal and provincial species at risk databases and information sources such as SARA, COSEWIC, and BCCDC were consulted in planning the small mammal inventory, and three target species were identified as possible residents based on their status, distribution, habitat requirements and likelihood of occurrence: Pacific Water Shrew, the western sub-species of the Red-backed Vole, and the Lower Mainland subspecies of the Showshoe hare. All three targeted species are provincially red-listed as endangered or threatened and the Pacific Water Shrew is also listed by COSEWIC on Schedule 1 as threatened. Snowshoe hare and Red-backed Vole subspecies are federally considered data deficient and no formal status has been assigned to them. However, additional work on these species may significantly influence status designation. None of these species has ever been the subject of study in Richmond, thus information about their status on Lulu Island is very limited. However, habitat in the bog qualifies as highly suitable for the threatened Pacific Water Shrew (Craig 2003), and, based on captures in Burns Bog, the bog may also provide habitat for the western subspecies of the Red-backed Vole (Vennesland, pers. comm. 2005). Reported unconfirmed sightings of Snowshoe hare in the study area prompted interest in this species. Southern Red-backed Vole (western subspecies) Cletrionomys gapperi occidentalis BC Status: Red-listed Federal Status: not presently listed Abundance in survey area: never recorded in Richmond Habitat: prefer cool moist deciduous or coniferous forests. Use coarse woody debris and tree roots (Cannings et al. 1999). Locally observed: records from Vancouver and Burns Bog The status of C. g. occidentalis as a subspecies is derived from a species description in 1890 based on qualitative traits of one specimen from Chehalis County, Washington (Merriam 1890 in: Fraker et al. 1999). Although the taxon’s validity is questionable (Nagorsen 2000) recommends it continue to be treated as a taxon at risk until taxonomic analysis proves otherwise. Taxonomic analysis is planned for 2005 (Vennesland pers. com. 2005). Its known distribution in B.C. is limited to the lower Fraser Valley south of Burrard Inlet (Cannings et al. 1999). There are very few captures for this subspecies in B.C. Two historical observations exist from animals caught in Point Grey and Stanley Park, each more than 50 years ago. More recently, in the summer of 1999, seven individuals were trapped in Burns Bog (Fraker et al. 1999). The subspecies is at risk of extirpation in B.C., with limited suitable habitat in a highly fragmented and developed landscape, and only one known current population. The Lulu Island Bog remnants contain habitat similar to that in Burns Bog, and thus may be a potentially important habitat refuge. Pacific Water Shrew Sorex bendirii BC Status: Red-listed Federal Status: Threatened (SARA) Abundance in survey area: never recorded in Richmond Habitat: riparian specialist, associated with wet forests, marshes, areas adjacent to slow moving streams and ditches. Often in coniferous/mixed forested areas with coarse woody debris. Locally observed: all observations are within the lower Fraser Valley at low elevations, some in open ditches. The Pacific Water Shrew was federally listed as a threatened species in 2000 by COSEWIC, and the Species At Risk Act provides protection for the animal and its critical habitat. A recovery plan for the species has also been drafted. Provincial best management practices including protocols for sampling and assessing habitat suitability are also available. Observations are limited to the farthest southwest corner of the province extending as far east as Agassiz and north to the north shore of Burrard Inlet (Nagorsen 1996 in: Cannings et al. 1999). The shrew is a semi-aquatic riparian species (WLAP 2004). Irrigation and drainage ditches present throughout Lulu Island may act as vectors for movement and dispersal of the Pacific Water Shrew, and the wooded riparian areas along the ditches that surround each of the properties rank as highly suitable habitat according to the provincial habitat rating system (Craig 2003). Washington Snowshoe Hare Lepus americanus washingtonii BC Status: Red-listed Federal Status: subspecies not presently listedAbundance in study area: reported in 1984 park inventory, numerous subsequent suspected sightings as recent as April 2001 Habitat: prefer dense coniferous/mixed forest with abundant understorey Locally observed: less than five known occurrences in region, potential capture in Burnaby at a wildlife rescue shelter in 2003 (Thunstrom 2004). Observances are restricted to lower Fraser Valley (Nagorsen 1990, as cited in Cannings et al. 1999). This species, like the Southern Red-backed Vole and Pacific Water Shrew, is also threatened in B.C. due to a restricted range within a highly developed landscape (Cannings et al. 1999). Also, like the Southern Red-backed Vole, the subspecies’ validity is uncertain, but it is still treated as a taxon at risk. Until recently the hare was thought to be extirpated in this region as there were no recent confirmed sightings post 1970??? A specimen was found during the 1984 Richmond Nature Park inventory, but has since gone missing and its identity remains unconfirmed. The thick understoreys and food sources that the hares favour are abundant in the study area, and the area is known to host other lagomorph species including domestic rabbits and Eastern Cottontails (Sylvilagus floridanus mearnsii) (Bell 1984). 17.4 Methods In March 2004, The Richmond Nature Park Society obtained a permit for live trapping of small mammals. Trapping began in early August 2004 and continued until early December 2004. Trapping methodology followed the guidelines set out by the Resources Inventory Committee wherever feasible (RISC, 1998). The objective of the study was to survey and document the small mammal composition of the Lulu Island Bog, with a focus on insectivores, rodents and hares. To achieve this objective, a general inventory for all species present and a targeted inventory for three at-risk species were both carried out. Additionally, an owl pellet survey was conducted and scat, pellets, and bones were collected incidentally for the duration of the field season. Wherever possible, diagnostic bones and skulls found in the pellet and scat samples were identified to gain information on small mammal species that may inhabit in the park. Voles and shrews were examined most closely in an effort to determine the presence of the listed Southern Red-backed Vole and Pacific Water Shrew. Prior to fieldwork, habitat mapping was performed by Habitat Biologist Libor Michalak in order to stratify the study site into broad habitat units based on vegetation mapping work completed by University of British Columbia Geography students (Klinkenberg, 2004) and aerial photograph interpretation (date and scale of photos here). Trapping was planned to sample each of the habitat units for the general inventory, and to focus on the particular habitat units associated with each of the targeted inventory species. Seasonality and timing were also factored in. For example, August is generally deemed to be the best month to trap for Red-backed Vole, so trapping at that time focused on this species. Trap locations were marked using a Global Positioning System unit. A variety of trap types and associated methods were employed.
Body length and tail length were measured for each trapped animal, and photos were taken to document species and for individuals that were difficult to identify or were of special interest. Additional diagnostic measurements, such as hind foot length, were taken dependent on species, according to Nagorsen (2002). Mortalities were noted, and a subset of specimens were kept for deposit at the Cowan Vertebrate Museum at the University of British Columbia. 17.5 General Inventory Trapping was planned such that each of the habitat units would be sampled for the general inventory. Traps were placed in representative sections of each habitat unit based on a visual assessment of the habitat structure and potential species’ life history traits Nagorsen, 1996; RISC, 1998). Pitfall traps and transects of Sherman and/or Longworth traps were used to sample the units. 17.6 Targeted Inventory 17.6.1 Southern Red-backed Vole (western subspecies) All seven Southern Red-backed Voles caught in Burns Bog were trapped in the same “Pine Woodland” habitat type, typified by Shore Pine (Pinus contorta var. contorta) and birch (Betula papyrifera) overstorey and a dense salal (Gaultheria shallon) understorey (Hebda et al., 2000, Robertson pers. comm.. 2004). Other studies have also recorded higher abundances of Red-backed Voles in forest stands with more structurally diverse understoreys (Sullivan et al. 2001). Similar habitat exists in the RNP, and trapping for the vole focused on these areas. Trapping for the vole began in August which is the recommended period because juveniles are dispersing. The habitat units were used as guidelines for trap placements, but ultimately transects were placed based on finer scale ground-truthing of the park properties for the most suitable habitats. Dense salal understorey and a significant canopy were used as indicators of habitat suitability, thus transects were laid under birch as well as pine canopy, where salal understorey was dominant. More experimental transects were also placed in habitats dominated by Labrador tea (Rhododendron groenlandicum) and bog blueberry (Vaccinium uliginosum ssp. occidentalis) among patches of Shore pine, tall European birch (Betula pendula) shrubs and cultivated blueberry (Vaccinium corymbosum). 17.6.2 Pacific Water ShrewKnowledge of this species’ life history and habitat use is limited. Trapping strategy and methods were adopted from Craig (2003), Craig (2003a) and in consultation with Michalak (2004) and Vennesland (pers. comm. 2004). Trapping focused around the permanent waterbodies in the park, and prioritized those that were more likely connected with other waterways in Richmond. Pitfall traps and transect drift fences were set every 15 metres perpendicular to the water’s edge. Where possible, fences followed habitat features such as coarse woody debris that the shrews may use as cover. Pacific Water Shrews are endangered and susceptible to mortality in traps. To minimize the chances of mortality, riparian traps were checked at eight hour intervals and closed during heavy rainfall. 17.6.3 Snowshoe HareThe Snowshoe Hare was reported in the west property of the park in an inventory by Bell (1984). There have been subsequent sightings in recent years (Griffith pers. comm., 2004). Trapping focused on these areas where there had been recent sightings, and other areas with habitat similar to those where there had been sightings. Traps were placed at the edges of openings and along runways under shrubs. Hare trap cages were placed in the RNP west and DND properties only. 17.6.4 Pellet and Scat Collection and AnalysisSamples were collected between July and October 2004 in the DND and the two park properties. The pellet survey focused on areas of the three properties with mature hemlock trees. Four time-constrained searches in these areas were conducted during July and August 2004. Pellets and scat were also collected incidentally in the three properties in conjunction with other mammal trapping efforts. Small mammals that were identified in owl pellets or coyote scat cannot be directly linked to the study area due to the transient nature of these two predators. However it is likely that the predators are catching a portion of their prey items within the study area boundaries, as small mammals are common in the study area. Thus the pellet and scat analysis does augment the data collected by other means such as live trapping. Pellets and scat were dissected and all bones were removed for identification. Skulls provide the most accurate means of identification and were the only bones used to identify to genus or species. The general dental formula was used to determine genus, and details of the cheek teeth, as outlined by Maser and Storm (1970), were used to determine species. Other bones aided in the enumeration of small mammals in the pellets or scat but were not used for identification beyond genus. 17.7 Results 17.7.1 Live trappingBetween July and December 2004, 44 000 trapping hours of effortwere expended across the three properties and across the habitat units. Pitfall, Sherman and Longworth traps were used on all three properties. The hare traps were placed on the DND and RNP properties, but not the RNP east. 148 individuals comprising seven species were caught. Deer Mice and Vagrant Shrews were the most frequently caught species, accounting for 69% (102 of 148) of all captures.
Table *** trapping effort in each of the properties 17.7.2 Species Accounts
Table 17.____: Total species captures in each of the properties 17.7.2.1 Deer Mouse ( Peromyscus maniculatus)A total of 34 Deer Mice were caught, 8 in the DND and 26 in the east property. The east is the most forested of the three properties, with a canopy of predominantly birch and smaller components of hemlock and pine. This species was caught almost exclusively in forested habitats dominated by birch, with low shrub cover dominated by salal. All 26 individuals in the east were caught in this habitat type, and of the 8 individuals caught in the DND, 5 were caught in this habitat type along the north edge of the property. This correlates closely with the results of the Burns Bog trapping, which found 69% of all Deer Mouse Captures in mixed coniferous or decidous forest habitats (Fraker et al. 1999). This species is abundant throughout most of North America across a range of habitat types (NatureServe 2004). 17.7.2.2 Vagrant/Dusky Shrew (Sorex vagrans vagrans/Sorex monticolus)The identification of most shrews is based on dental characteristics (Nagorsen, 2002). Distinguishing the Vagrant Shrew from the Dusky Shrew (Sorex monticolus) is impractical with live animals in the field, thus judgement was reserved and individuals were recorded as Vagrant/Dusky Shrews. Vagrant/Dusky Shrews were found on all three properties, and were the most commonly caught species. The Vagrant Shrew is also reported in the 1984 inventory of the west property (Bell 1984). Both species are abundant provincially and in North America. 17.7.2.3 Townsend’s Vole ( Microtus townsendii) There were difficulties identifying the Townsend’s Vole due to the challenges of distinguishing juveniles from dark-pelaged Southern Red-backed Vole. Although the literature describes external distinguishing features such as dorsal pelage colouration and tail colouration (Nagorsen, 2002), there were numerous cases where trapped animals could not be clearly defined by any external characteristics. Weights and sizes of the two species overlap. In an analysis of specimens at the Cowan Vertebrate Museum, one confirmed specimen of Clethrionomys gapperi occidentalis in the collection exhibited somewhat uniform brown pelage typical of the Townsend’s Vole instead of the reddish dorsal pelage that is the most distinctive external characteristic of the Southern Red-backed Vole. Furthermore, some captured individuals identified as Townsend’s Voles by their size, weight and colouration had white hairs on the underside of their tails, a distinguishing characteristic of the Southern Red-backed Vole (Nagorsen 2002). This raised further questions about the possibility of certainty in specimen identification. Most of the individuals caught in the bog fell within the range of overlapping sizes and weights. 12 of the 21 voles caught were not identified to species. Ranges of species characteristics (add source)
Voles were trapped most commonly (16 of 21 individuals) on the east property. All of the Townsend’s Voles caught in the east property were in forested habitats with dense salal understory, as were all of the unidentified voles also caught in the east. The individual caught in the DND was found in dense heather and Labrador tea habitat with scattered cultivated blueberry and birch shrubs and lacking tree canopy. This species is commonly associated with meadows, marshes, and other herbaceous, open habitats (NatureServe 2004). Despite the availability of more open habitats such as the areas dominated by heather, Labrador tea, cultivated blueberry and native blueberry, it was found predominantly in forested habitats during this inventory. This may be due to several factors. First, more trapping hours were expended in forested habitats than in more open habitats. It is also possible that the heath-dominated habitat does not provide the same features or forage for this herbivore as more herbaceous meadows and marshes do, and consequently, their use of heath habitat is limited. The occurrence of our voles in habitat less-preferred by Townsend’s augmented the uncertainty of species identification. Forested habitats had been targeted as likely Southern Red-backed Vole habitat due to their similarity to the habitat type that all seven Southern Red-backed Voles were found in at Burns Bog. The Townsend’s Vole is abundant in B.C. and its range extends from B.C. through Washington and Oregon to California. 17.7.2 4 Douglas’ Squirrel (Tamiasciurus douglasii mollipilosus) Douglas’ Squirrels are common in the west property and can be seen around the bird feeder. Two individuals were trapped, one in the DND and one in the west property. The species is common in B.C. and is also found in the western U.S. It is typically found in coniferous forest habitats. 17.7.2.5 Eastern Grey Squirrel (Sciurus carolinensis) The Eastern Grey Squirrel is native to eastern North America where it is common throughout its range. It is an exotic species in western Canada and the western U.S., introduced to this area in 1914 in Stanley Park. Its range in the region has been growing since then. Park staff first began noticing the Eastern Grey Squirrel in the nature park approximately 5 years ago. Its population appears to be growing quickly in the park, and it is now easily seen around the pond and bird feeder in the west property. Only one individual was caught in the west property, although the species is suspected of having frequently visited the hare traps and taken bait without setting the traps off. 17.7.2.6 Black Rat (Rattus rattus)The Black Rat is an introduced species often associated with ships, ports and other non-natural environments. It is also sometimes found in natural habitats. This species was trapped 18 times in the DND and east property. All but one of the captures were along edges of disturbed habitat. The 9 captures in the DND were along the edges of the north south lane and the south edge of the park, and 11 of the 12 captures in the east were near the peripheral ditch that separates the park from Jacombs Road and the Richmond Auto Mall. 17.7.2.7 Striped Skunk (Mephitis mephitis) One Striped Skunk was caught
in a hare trap on the west property. The Striped Skunk is a common
sight in the neighbourhoods of Richmond and Vancouver. It is common
throughout much of North America and can exist in a range of habitat
types. 17.7.3 Pellet and Scat Collection and Analysis Individuals of some owl species may have a favourite perch where they regurgitate pellets and this behaviour can result in several pellets at one location. Although owl pellets were often found in groups, each pellet was treated as an individual sample. There were a total of 36 (21 owl pellets, 14 coyote scat and 1 of unknown origin) individual samples. The majority of the skulls that were identifiable were in the Cricetidae family and sub-family microtinae. Evidence of Microtinae was present in 16 of 36 samples and of those that were identifiable to species, all were Townsend’s Voles. Four samples contained skeletal remains of members of the shrew family (Soricidae) however extensive damage to these skulls precluded identification to species. An individual in the Sciuridae family was identified by cheek teeth but could not be identified to species. 17.7.2 Other MammalsThere are additional mammals that have been recently sighted, photographed or whose signs are evident in the park. 17.7.2.1 Eastern Cottontail (Sylvilagus floridanus mearnsii)Macqueen (2004) photographed an Eastern Cottontail along the edge of the parking lot on the east property. The species can be observed elsewhere in Richmond and the Lower Mainland. It is an introduced species from eastern North America. 17.7.2.3 Coast Mole (Scapanus orarius orarius) The Coast Mole was reported by Bell in the 1984 inventory of the Richmond Nature Park, and nature park staff has collected numerous dead specimens found in the park over time. Signs of the mole, such as molehills, are common along the trails of the west property. The mole is abundant in the southwestern corner of B.C. and its range extends south into northern California. 17.7.2.4 Muskrat (Odonatra zibethicus osoyoosenisis) Bell (1984) also cites an unconfirmed observation of a Muskrat. Over 2002 and 2003, two Muskrats were resident in the pond on the west property, but there have been no sightings around the pond since a dead Muskrat on Westminster Highway was found in the summer of 2004. However, Nature Park naturalist Hugh Griffith has since observed fresh tracks and excavations along the east ditch of the west property (Griffith 2004). Muskrats inhabit the ditches and sloughs throughout Richmond, and will be a potential resident in the study area as long as the network of ditches in Richmond continue to provide suitable habitat and links to the study area. The Muskrat is extant across most of North America. 17.7.2.5 Coyote (Canis latrans latrans) Coyote scat is common on all 3 properties, and was collected during the trapping period for analysis of small mammal bones. Griffith (2004) reports finding a Coyote den in the northeast corner of the west property in September 2000. Coyotes are occasionally observed in many parts of the Lower Mainland. They are found in most of North America. 17.7.2.6 Black-tailed Deer (Odocoileus hemionus columbianus) Black-tailed Deer were last sighted in April and May of 2004 (Bauder, pers. comm. 2005) in the west property and tracks were observed in September in the DND property (Klinkenberg, pers. comm. 2004). Deer are more commonly observed in the farmlands of the east end of Lulu Island, and around the greenspaces between Number 6 Road and Number 7 Road at their southern ends along the river. New development and an expansion of the nearby dump have resulted in fewer recent sightings (Klinkenberg, pers. comm. 2004). Deer probably use the bog habitat periodically as part of larger movements around Richmond. There are no studies of deer populations or movements in Richmond (Evans, pers. comm. 2005), but continued development and shrinking greenspaces will have negative impacts on deer and may threaten the viability of a persisting population on Lulu Island. The columbianus subspecies of the Black-tailed Deer in B.C. is found west of the Coast Mountains in the southern half of the province and on most of the coastal islands. 17.7.2.7 Raccoon (Procyon lotor) Raccoons are another common
omnivore that is very capable of adapting to developed environments.
They are occasionally sighted in the park and are common in Richmond
and throughout south coastal B.C. (WLAP 1992). Raccoons are found in
most of North America. 17.8 Discussion 17.8.1 Species at RiskUntil very recently, the Greater Lulu Island Bog was largely undisturbed. Historical descriptions and photos (Klinkenberg and Klinkenberg 2001) indicate it was virtually treeless. Early surveyors recorded only occasional small and stunted shore pines. The portion of the bog that comprises the study area would not have provided forested or riparian habitat, and many of the habitat attributes identified in research that the vole, shrew and hare are associated with would not have been historically present at this site. Thus, the study area may not have historically hosted populations of the three targeted species at risk. Although Southern Red-backed Voles were found in Burns Bog Hebda et al. (2000) suggest that they are a relict population isolated by deforestation. They may be more closely associated with the forested habitats of Burns Bog than bog habitats. Only when the city began draining the bog via perimeter ditches and surrounding areas were developed, facilitating colonization by forest plants and agricultural/horticultural cultivars such as European birch in the bog remnants, did riparian, shrub and forest habitats start to evolve. Concurrent with this, evolution was continued development on Lulu Island that resulted in widespread natural habitat loss and fragmentation of remaining natural habitats. Hence, it is possible that, although suitable habitats for the vole, shrew and hare are now present in the bog remnants, dispersal into these remnants may be non-existent, limited or periodic due to fragmentation, habitat loss and a lack of source populations nearby. For example, past studies have characterized the Red-backed Vole as a poor colonizer of island habitats with low immigration rates and low rates of successful colonization (Crowell 1973) (Mills 1995). These may also factor into the potential occurrence of this species in the bog. It is also possible that the species are present here but were not detected. For example, in a small mammal survey of 55 sites comprising 19,000 trap nights, Zuleta and Galindo-Leal (1994) did not catch any Southern Red-backed Voles and trapped only three Pacific Water Shrews. The trapping effort expended by Fraker et al. (1999) in Burns Bog did not result in any Pacific Water Shrew captures, even though owl pellet analysis identified a Pacific Water Shrew skull that may have come from the bog (Fraker et al. 1999). These results could have several important implications for the results of this inventory. First, it may indicate that the species is rare within its range even in suitable habitats (Fraker et al. 1999). Second, the shrew may not be easily trapped with existing trap types even when suitable habitats are targeted. 17.8.2 Pellet and Scat AnalysisBones and/or feathers or fur were found in all but two of the samples, which suggests that small mammals and birds play a significant ecological role as prey items for predators. The relative abundance of small mammal species identified in the pellet and scat analysis does not closely correspond with the trapping results. Deer Mice and Vagrant/Dusky Shrews, the two most commonly caught small mammals, are uncommon in the pellet and scat analysis results. This may be due to several factors. Soricidae skulls are delicate and easily crushed, rendering them unidentifiable. It is likely that shrews are a prey item for coyotes and owls, but unlikely that their remains in pellets and scat are preserved in identifiable form. Furthermore, coyotes and owls are likely catching some of their small mammal prey outside of the study area boundaries. The relative abundance of small mammal species may differ outside the study area. 17.9 Recommendations The Lulu Island Bog is used by populations or individuals of the majority of the mammal species known in Richmond. Together, the three properties comprise the largest remnants of natural habitat on Lulu Island. The remnant boglands are an important site for the preservation of wildlife on the island, and the City of Richmond has identified all three properties as Environmentally Sensitive Areas (see map). Greenspaces around Richmond are increasingly subject to development as the city grows, and remnant habitats such as the park and DND properties may become more important as refuges if the extent of greenspaces continues to shrink. These properties warrant protection based on their significance in this regard. Protected status for the DND property would ensure continuation of its capacity to sustain populations of numerous small mammals. It would also provide valuable habitat for larger mammals such as coyote and deer, which need natural habitat refuges and use the DND in conjunction with the park properties, and as part of larger home ranges. Anecdotal reports from DND staff of regular deer sightings on the property may indicate that deer use the DND property more frequently than the park, which would provide further reason for the protection of this site. Given the rarity of the three species at risk and the lack of suitable habitat in this highly developed region, preservation of the habitat that exists in the Lulu Island Bog is further warranted based on the potential of their presence. In particular, the presence of highly suitable habitat for the Pacific Water Shrew in the study area should result in the implementation of the habitat protection guidelines set out in the provincial draft of the Best Management Practices Guidelines (Craig and Vennesland 2004). As a COSEWIC threatened species, the federal and provincial governments have an obligation to ensure adherence to these protective measures for the animals and their critical habitat. Craig and Vennesland’s (2004) habitat protection guidelines that have relevance to the study area include recommended 100 metre buffer zones on each side of watercourses and wetlands that are suitable habitat or habitat capable of being suitable. Within the buffer zones, only minimal low impact disturbance such as walking trails are recommended. The guidelines also propose the restoration of low suitability habitat to higher suitability habitat. These measures are pertinent for the east ditch of the west property and the west ditch in the east property. The ditch edges closest to the highway are dominated by grasses and invasive species such as Himalayan blackberry (Rubus discolor), a species which does not provide optimal habitat for Pacific Water Shrews. These are sites where restoration of native shrub and tree species would be suitable, or, at the least, where further disturbance such as grass mowing or clearing should be avoided to allow further re-vegetation of the riparian zone. Roads, bridges and other crossings within suitable Pacific Water Shrew habitat are also discouraged. These incursions fragment habitat and facilitate the establishment of invasive species (Craig and Vennesland 2004). Where crossings cannot be avoided, the guidelines advocate the use of bridges instead of culverts. Bridges can be designed to leave buffers on either side of the waterbody. The guidelines can help protect riparian and wetland habitat, increase or preserve the connectivity between habitats, and protect the waterbody and its ecological processes. These outcomes may be of benefit for many riparian and wetland species. to be added
A report of White footed Mouse in earlier park studies is no doubt an error and was most likely a Deer Mouse. REGIONAL PERSPECTIVE Small Mammals confirmed in Burns Bog (from Fraker et al. 1999) Pacific Water Shrew (skull) (confirmed--also confirmed
in nearby Serpentine Fen) Small mammals not confirmed in Burns Bog (Fraker et al. 1999) Long-tailed Weasel Mammals that are considered extirpated from Burns Bog (based on Gebauer 1999) Porcupine Mammals reported but unverified (based on Gebauer 1999) Townsend's Mole Leporids
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