The western red bat (Lasiurus blossevillii) is a medium-sized bat with fur that is usually mottled reddish and grayish, but can range from bright orange to yellow-brown. Whitish patches are seen near the shoulder and most fur hairs are frosted with white tips. Wings are long, narrow, and pointed. They have a distinct bib under the neck, which contrasts greatly with the jet-black wing membrane. Ears are 0.4-0.5 inches (11-13 mm) in length, low and rounded. Males are usually more colorful than females. The western red bat weighs 0.25-0.5 oz (7-15 g) and has a wingspan that is 11.4-13 inches (29.0-33.2 cm). Western red bats are mostly solitary, but may migrate in groups and forage in close association with others. Males and females migrate at different times and have different summer ranges. They normally migrate south in the winter and may be active in areas with temperatures as low as 55º-65ºF (12º-18ºC).
The western red bat is not federally listed as threatened or endangered. It was included in a draft list of Arizona Wildlife of Special Concern by the Arizona Game and Fish Department. According to the State of Nevada Comprehensive Wildlife Conservation Strategy, the western red bat is a Nevada Species of Conservation Priority and is protected and considered sensitive. In California, the western red bat is proposed as a Mammal of Special Concern. The Western Bat Working Group lists the western red bat as a species of “Red or High” priority, the highest priority available.
The western red bat was previously recognized as a subspecies of the eastern red bat (Lasiurus borealis teliotis). It was acknowledged as a separate species by most bat researchers between 1988 and 1995.
Breeding occurs from August to October and the female will store sperm until the following spring when fertilization begins. After a gestation of 60-70 days, a female gives birth generally to a litter of two offspring from late May to mid-June. Estimated time of young to fledge is between their third and fourth week.
Western red bats begin foraging 1-2 hours after dark and may continue into the following morning. They are known to feed 600-1000 yards from their roosting site and will forage from tree-top level to a few feet above the ground. Moths appear to be one of the main prey items but the bats also readily feed on flies, bugs, beetles, cicadas, ground-dwelling crickets, and hymenopterans. They use their wing membranes to capture prey and will sometimes land on vegetation to catch an insect. Red bats commonly forage near light sources, which attract insects. Echolocation is used to find prey, including narrow and broadband calls. When searching, they use long calls with a low pulse repetition of narrow band frequencies.
Known threats to red bats include birds of prey, roadrunners, opossums, and domestic cats. Woodpeckers and raccoons have been observed disturbing other tree-roosting bat species at their roosting sites. The greatest threat to western red bats in the southwestern United States is the loss of riparian habitat. Specifically, the Western Bat Working group has stated that the loss of cottonwood forests from desert riparian corridors may be the reason for the decline of the western red bat in those areas. These forests may be important to not only resident red bats, but also to migrants. Human-caused threats include barbwire fences and motor vehicles. Pesticide use in fruit orchards may also pose a threat to bats roosting at those sites. The negative image of bats by the public, such as the fear of rabies, should also be considered a threat.
Updated November 26, 2012
The historical range of the western red bat is believed to mirror its current range, where available habitat occurs, including the western portions of British Columbia, Washington, and Oregon, and western, central, and southern Nevada. The entire states of California and Arizona are considered within its range. The full extent of their range in Utah, Colorado, Wyoming, Idaho, Montana, New Mexico, and western Texas is not well known. Western Texas is also an area of overlap between western and eastern red bats (Lasiurus borealis), which occur in the central and eastern areas of the United States. Western red bat distribution continues throughout Mexico, Central America, and almost the entire continent of South America.
Click on the map below to see the distribution range of the western red bat using the interactive GIS map.
Historically, no red bats have been reported from the LCR. The closest record to the LCR was of 3 female red bats collected in July 1902 on Big Sandy Creek (50 miles east of Topock, AZ). However, in recent years, western red bats have been detected along the LCR during acoustic and capture surveys. In general, the western red bat appears to be rare along most of the LCR, but as surveys continue, more populations may be found. Information about acoustic surveys of bats can be found at the LCR MSCP Bats research and monitoring web page.
Western red bats prefer riparian woodland habitat. A study (found here) along the LCR compared bat acoustic activity within four riparian habitat types: cottonwood-willow, mesquite, Tamarisk, and marsh. Of these four habitat types, western red bat occupancy was significantly higher in cottonwood-willow compared to the others. Elevation of these habitats may vary from 1,900 to 7,200 ft (580 to 2,196 m). Roost sites range from a few feet off the ground to more than 40 ft high. Red bats prefer heavily shaded areas, which are open underneath, enabling them to drop into flight.
Like other members of the genus Lasiurus, western red bats primarily roost in trees. Specifically, in the southwestern United States, western red bats are found in desert riparian areas. Tree species in these areas may include but are not limited to Fremont cottonwood, Goodding’s willow, and sycamore. Although red bats may roost in any of these, they primarily roost in cottonwoods. They are also known to roost in shrubs in riparian habitats, as well as fruit tree orchards. If roosting in dense foliage, they can resemble dead leaves. Red bats were observed occasionally roosting in cave-like situations and in the boot of the saguaro cactus, a hardened area of scar tissue that forms a hollow shape inside the cactus from cavity excavation by woodpeckers.
LCR MSCP Conservation Measures
The Habitat Conservation Plan provides conservation measures specific to each species. Listed below are the species specific conservation measures for the western red bat. Click on the arrows to expand the table.
|WRBA1—Conduct surveys to determine species distribution of the western red bat|
Conduct investigations to identify the distribution of the western red bat in Reaches 3–5.
|WRBA2— Create 765 acres of western red bat roosting habitat|
Of the 7,260 acres of cottonwood-willow and honey mesquite to be created as covered species habitat, at least 765 acres will be designed and created to provide western red bat roosting habitat. Created roosting habitat will be designed and managed to support cottonwood-willow types I and II and honey mesquite type III. The LCR MSCP process for selecting sites to establish cottonwood-willow and honey mesquite as habitat for other covered species habitat will, based on the information collected under conservation measure WRBA1, give priority, when consistent with achieving LCR MSCP goals for other covered species, to selecting sites that are occupied by the western red bat in Reaches 3–5. As described in Section 5.4.3 in the HCP, created cottonwood-willow and honey mesquite land cover will be designed to establish stands that will support a substantially greater density and diversity of plant species that will provide roost trees and that are likely to support a greater abundance of insect prey species than is currently produced in the affected land cover types.
|MRM1—Conduct surveys and research to better identify covered and evaluation species habitat requirements|
Conduct surveys and research, as appropriate, to collect information necessary to better define the species habitat requirements and to design and manage fully functioning created covered and evaluation species habitats. This conservation measure applies to those species for which comparable measures are not subsumed under species-specific conservation measures (Section 5.7 in the HCP). They are not applicable to species for which habitat would not be created under the LCR MSCP Conservation Plan, such as the desert tortoise, relict leopard frog, humpback chub, and threecorner milkvetch.
|MRM2—Monitor and adaptively manage created covered and evaluation species habitats|
Created species habitats will be managed to maintain their functions as species habitat over the term of the LCR MSCP. Created habitat will be monitored and adaptively managed over time to determine the types and frequency of management activities that may be required to maintain created cottonwood-willow, honey mesquite, marsh, and backwater land cover as habitat for covered species. This conservation measure applies to those species for which comparable measures are not subsumed under species-specific conservation measures (Section 5.7 in the HCP). They are not applicable to species for which habitat would not be created under the LCR MSCP Conservation Plan, such as the desert tortoise, relict leopard frog, humpback chub, and threecorner milkvetch.
|CMM1—Reduce risk of loss of created habitat to wildfire|
Management of LCR MSCP conservation areas will include contributing to and integrating with local, state, and Federal agency fire management plans. Conservation areas will be designed to contain wildfire and facilitate rapid response to suppress fires (e.g., fire management plans will be an element of each conservation area management plan).
|CMM2—Replace created habitat affected by wildfire|
In the event of created-habitat degradation or loss as a result of wildfire, land management and habitat creation measures to support the reestablishment of native vegetation will be identified and implemented.
|AMM1—To the extent practicable, avoid and minimize impacts of implementing the LCR MSCP on existing covered species habitats|
To the extent practicable, establishment and management of LCR MSCP–created habitats will avoid removal of existing cottonwood-willow stands, honey mesquite bosques, marsh, and backwaters to avoid and minimize impacts on habitat they provide for covered species. Temporary disturbance of covered species habitats, however, may be associated with habitat creation and subsequent maintenance activities (e.g., controlled burning in marshes and removal of trees to maintain succession objectives). LCR MSCP conservation measures that could result in such temporary disturbances will, to the extent practicable, be designed and implemented to avoid or minimize the potential for disturbance. In addition to implementing AMM3 and AMM4 below, these measures could include conducting preconstruct ion surveys to determine if covered species are present and, if present, implementing habitat establishment and management activities during periods when the species would be least sensitive to those activities; or redesigning the activities to avoid the need to disturb sensitive habitat use areas; staging construction activities away from sensitive habitat use areas; and implementing BMPs to control erosion when implementing ground disturbing activities.
|AMM5—Avoid impacts of operation, maintenance, and replacement of hydroelectric generation and transmission facilities on covered species in the LCR MSCP planning area|
To the extent practicable, before implementing activities associated with OM&R of hydroelectric generation and transmission facilities, measures will be identified and implemented that are necessary to avoid take of covered species where such activities could otherwise result in take. These measures could include conducting surveys to determine if covered species are present and, if so, deferring the implementation of activities to avoid disturbance during the breeding season; redesigning the activities to avoid the need to disturb covered species habitat use areas; staging of equipment outside of covered species habitats; delineating the limits of vegetation control activities to ensure that only the vegetation that needs to be removed to maintain infrastructure is removed; stockpiling and disposing of removed vegetation in a manner that minimizes the risk of fire; and implementing BMPs to control erosion when implementing ground disturbing activities.
|AMM6—Avoid or minimize impacts on covered species habitats during dredging, bank stabilization activities, and other river management activities|
To the extent practicable, before initiating activities involved with river maintenance projects, measures will be identified and implemented that avoid or minimize take of covered species where such activities could otherwise result in take. Such measures could include alternative methods to achieve project goals, timing of activities, pre-activity surveys, and minimizing the area of effect, including offsite direct and indirect effects (e.g., avoiding or minimizing the need to place dredge spoil and discharge lines in covered species habitats; placing dredge spoils in a manner that will not affect covered species habitats).
Research and Monitoring Activities
The LCR MSCP conducts a variety of research and monitoring activities along the LCR encompassing both MSCP and non-MSCP species. For a complete list of all activities, please see the Research and Monitoring Activities web page.
The following list includes different research and monitoring activities for bats. Click on the link for more information.
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