Stressors/Threats

Relevance to Species

HABITAT LOSS

breeding

Historically many records were from riparian areas, but current and recent records are mostly from upland. Historic loss of breeding habitat is deemed a major factor in loss of this species. Breeds in areas with fairly dense and diverse native vegetation, but may include some non-natives as well. Requires holes, mostly saguaro holes, for nest site, and abundant food. Needs a home range of approximately 35 acres for breeding season.

dispersal

Females disperse over a long distance in search of males. Males disperse from natal area to new suitable territory, usually close to natal area. Dispersal occurs July-November. Loss of vegetation diversity and structure, especially trees, results in disruption of connectivity and may impede dispersal.

foraging

size of foraging area is unknown, may be related to available food supply, differs seasonally and in life cycle of species; diversity of resources is important

plant locations

N/A

wintering

winters in this area, needs foraging and roosting sites, winter food supply may be critically important; females rest in dense mesquite in winter

migratory stops

does not migrate, but needs suitable wintering areas and places to rest during dispersal periods

diurnal preferences - day, temporary

may use some short-term roosts

diurnal preferences - day, long-term

not applicable

diurnal preferences - night

unknown

fire threat

fire may cause loss of habitat, especially good nest sites

HABITAT ALTERATION

prey

Consumes diverse prey: insects, lizards, rodents, small birds. Habitat diversity provides for a variety of prey items, anything that reduces diversity is bad. Rock piles may be harborage for prey species.

HABITAT ALTERATION continued

nest sites

uses woodpecker holes in saguaros and (rarely) other trees; loss of mature saguaros or loss of woodpeckers would result in habitat alteration which would render areas unsuitable

vegetation composition/density

prefers high density vegetation with multiple layers; loss of one or more layers, by fire, grazing, flood, or mechanical impacts would be bad

habitat conversion

conversion to annual or invasive grassland reduces diversity and increases fire damage

escape cover

needs some protection from raptors, usually in the form of dense vegetation

fragmentation

fragmentation of historic habitat may have led or contributed to endangerment of this species; currently benefits from connectivity for dispersal

invasive plant species

invasion by mesquite and bufflegrass is probably bad for this species, because it reduces vegetation diversity and can lead to fires

invasive animal species

cats are known to prey on owls

habitat rehabilitation potential

questionable: anything that enhances vegetation diversity is probably good; habitat rehabilitation to enhance connectivity is probably a practical approach

contaminants

unknown

nutrient enrichment

probably irrelevant

water accessibility

owl is loosely associated with water, but this may be just that water enhances prey and cover

drought

may result in reduction of prey populations

flood

not considered a problem

groundwater depletion

may have led to loss of suitable habitat in the past, and may impede restoration of suitable habitat

root zone water loss

may have led to loss of suitable habitat in the past, and may impede restoration of suitable habitat

artificial water sources

may be beneficial by enhancing prey and cover

infiltration

not a problem

HABITAT ALTERATION continued

runoff

not a problem

edge effects

may increase predation by cats, dogs, and kids

fire threat

may alter habitat adversely

water quality - turbidity

apparently irrelevant

water quality - salinity

apparently irrelevant

water quality - conductivity

apparently irrelevant

water quality - dissolved oxygen

apparently irrelevant

water quality - effluent

apparently irrelevant

sheetflow disruption

unknown

flow rate

apparently irrelevant

land use history

prefers areas of dense vegetation with saguaros and high vegetation diversity; anything that lowers density or diversity, such as grazing, mining, development, fire, etc. is considered bad

roads - dust

not considered a problem

roads - erosion

may have adverse impacts on prey availability

roads - surface water diversion/ponding

may have adverse impacts on prey availability

roads - asphalt/contaminants

unknown

SPECIES CHARACTERISTICS

dispersal mechanism

Females disperse over a long distance in search of males. Males disperse from natal area to new suitable territory, usually close to natal area. Birds fly short distances, from tree to tree. Dispersal occurs July-November. Loss of vegetation diversity, especially trees, results in disruption of connectivity and dispersal. Intense activity of people such as construction and maintenance may impede or influence dispersal and may make it difficult for females to locate males.

behavior traits

not known to be a problem

habitat rehabilitation potential

May be fairly easy to increase and/or improve connectivity by managing vegetation. May be possible to increase or improve breeding habitat by working to maximize vegetation diversity and prey base.

SPECIES CHARACTERISTICS continued

colonization potential

Unknown, but probably very limited by connectivity and suitable habitat

effective population size

unknown

total population size

unknown

fecundity

not considered a problem, although long-term survival may be a problem

knowledge/data on species

essentially nothing is known about demographics or population dynamics

seasonal specialization

winter availability of prey may be important

captive breeding/translocation potential

unknown, but may be a useful approach

genetic isolation

may be a problem

inbreeding

may be a problem

diurnal specialization

not considered to be a problem

off-site mortality - migratory

no information is available

off-site mortality - from surrounding land uses

no information is available

breadth of resource use

appears to have specialization to a narrow range of resources, but this is not well understood yet

sensitivity to disturbance

considered sensitive to disturbance, although some individuals habituate to frequent disturbance

adaptability

fairly limited in habitat selection

charisma

Fairly charismatic and popular, or unpopular scapegoat, depending on one's point of view

INTERSPECIFIC FACTORS

predation

Highly susceptible to predation by raptors, does not thrive in areas with high raptor concentrations or perches for raptors

disease

probably susceptible to West Nile Virus, but this is not certain; other diseases are unknown

pollinators/seed dispersers

NA

INTERSPECIFIC FACTORS continued

competition

may be subject to competition for nest cavities and prey

brood parasitism

not considered a problem

domestic/feral animals

may be preyed on by cats and harassed by dogs

invasive species

effects unknown, invasive plants alter habitat adversely

ANTHROPOGENIC FACTORS

edge effect

may increase susceptibility to predation, roadkill, and shooting

disease

unknown, but see above

fire threat

fire may cause loss of habitat, especially good nest sites

off-road vehicles - dust

not considered a problem

off-road vehicles - erosion

not considered a problem

off-road vehicles - noise

disturbance may be a problem if frequent; may increase fire frequency

mining

not considered a problem

passive recreation

not considered a problem except that bird watchers may harass

grazing - vegetation impacts

may be harmful if it reduces vegetation diversity

grazing - soil impacts

not considered a problem

collection/hunting

not considered a problem, except illegal target shooting

herbicides

not thought to be a problem, except as they may affect prey base

insecticides

not thought to be a problem, except as they may affect prey base

pesticides - impacts to species

not considered a problem, species is short-lived, does not have a known bioaccumulation problem

pesticides - impacts to prey

insecticides may reduce prey base; present use of rodenticides may be a problem for this species

direct take/mortality

not considered a problem, except illegal target shooting

ANTHROPOGENIC FACTORS continued

noise

may be a problem if frequent disturbance occurs

light

effects unknown; high intensity lights, as used by Border Patrol, may be disruptive

movement

may be a problem if frequent disturbance occurs

landscaping

could be beneficial if high density vegetation with structural diversity

invasives

buffelgrass may be bad, mesquite invasion is bad

domestic/feral animals

may be a problem, especially predation by cats

dumping

not considered a problem

undocumented immigrants

may cause fires that result in habitat loss; also may cause repeated disturbance in nesting areas

increased road density

not considered a problem except that it may result in loss of habitat

road kill

may be a problem, not well documented

electrocution on powerlines/towers

not considered a problem but birds may occasionally collide with towers

CONNECTIVITY

fragmentation

needs a high level of connectivity, with trees in close proximity to each other and high density, to facilitate dispersal

barriers

wide roads, washes, and tall fences may be barriers

traffic volumes

may be problematic by increasing roadkill risk

wash incision

unknown

corridor width

unknown, but wider is probably better; may be limited by wash width

habitat patchiness

connectivity is considered crucial

riparian/upland connection

unknown, but complex issue

road crossings

may be hazardous

road width

unknown, but AGFD report on this issue is due soon

vegetation next to roads

may be a problem if it increases roadkill risk

Stressors/Threats

Relevance to Species

HABITAT LOSS

foraging

size of foraging area is unknown, but will forage over large distances; thought to prefer "edges" of habitat

wintering

winter roosts are generally caves or mines, threatened by closure

migratory stops

roosts are necessary for migrants

diurnal preferences - day, temporary

unknown and unlikely

diurnal preferences - day, long-term

caves and mines are extremely important

diurnal preferences - night

needed, includes bridges, buildings, drainage culverts?, and other unknown

fire threat

probably minor

HABITAT ALTERATION

prey

moths, 3-10 mm, Noctuidae; but includes other insects; loss of prey= loss of bats

nest sites

maternity roosts critically important

vegetation composition/density

important as source of prey; protect riparian and other edges

fragmentation

potentially does not matter, it lives in a fragmented landscape

invasive plant species

unknown, probably affects prey base

habitat rehabilitaion potential

limited for roosts; conditions needed are generally unknown; gating roosts could be beneficial

contaminents

unknown; there is some indication that bats can acquire toxic materials in roosts, and considerable evidence that some species can acquire toxic doses of insecticides by consuming contaminated prey

water accessibility

drinks from and forages over water; very small water sources are used, large water bodies have not been surveyed; could benefit by vegetation around water

artifical water sources

drinks from and forages over water; very small water sources are used, large water bodies have not been surveyed; could benefit by vegetation around water

edge effects

prefers foraging along edges

fire threat

may affect prey

water quality - turbidity

broadly tolerant of water quality

flow rate

may prefer still or slow moving water

roads - surface water diversion/ponding

may be beneficial

SPECIES CHARACTERISTICS

behavior traits

sensitive to disturbance at roosts

habitat rehabiitation potential

potential to increase prey base; could benefit by gating mines and caves; experiment with creating habitat?

fecundity

1 young per year, fecundity is low as with most bats

captive breeding/translocation potential

no success with moving from roosts

inbreeding

very low variability suggests inbreeding or small gene pool

off-site mortality - from surrounding land uses

could be driven from areas by renewed mining, urban expansion, human disturbance

sensitivity to disturbance

highly sensitive; outreach to recreational cavers and mine explorers is needed

adaptibility

not very adaptable to some changes, especially loss of roosts

charisma

mixed bag: bats have had a major change in public image in past two decades but some people still fear or hate; need to empasize that they eat pest insects

INTERSPECIFIC FACTORS

predation

limited knowledge; may be subject to predation by cats but this is not likely

disease

rabies may affect; others unknown

competition

unknown; has been found in roosts with other species

domestic/feral animals

may be preyed on by cats, but this is not likely

ANTHROPOGENIC FACTORS

edge effect

edges are prefered foraging sites

off-road vehicles - dust

ORVs may be a problem because they get people to roost sites and result in disturbance

mining

renewed mining in areas with old mines may result in disturbance or loss of roosts

passive recreation

disturbance of roosts; should route trails to avoid roosts

grazing - vegetation impacts

may affect prey base

collection/hunting

not thought to be a problem

herbicides

not thought to be a problem, except as they may affect prey base

insecticides

impacts have been reduced over time, but still may be a problem

pesticides - impacts to species

impacts have been reduced over time, but still may be a problem

pesticides - impacts to prey

this could be significant

direct take/mortality

little effect except from mine hazard abatement practices, which could be serious impacts; road paving and de-icing may affect

light

bright lights near roosts may affect

landscaping

native plants could provide beneficial opportunities for habitat improvement

dumping

may affect if in roost sites

undocumented immigrants

may affect when they use caves and mines for shelter or dumping grounds

increased road density

may be a problem, low-flying bats could get hit by cars while foraging along road edges

road kill

may be a problem, low-flying bats could get hit by cars while foraging along road edges

CONNECTIVITY

barriers

large cities with abundant lights could be barriers

traffic volumes

increased volume could lead to increased road kill

wash incision

could create roost sites but could also take some away

corridor width

buffers along washes would be good but width unknown

habitat patchiness

depend on what is around them; patchiness could be good because it could increase insect diversity

riparian/upland connection

bridges could be improved as bat roosts

road crossings

could be opportunity for foraging or hazard due to roadkill

vegetation next to roads

could be opportunity or hazard; recommend not planting edges along larger and faster roads, allow space between trees and roads