Dr. Sawaya Podcast and Publication Flashcards
What was the concern with the relationship between the bears habitat and the highway in Banff National Park?
- concerns over bears being able to mate with other bears on the opposite side of the road
- the inability to do so would decrease genetic diversity, and lead to isolation and inbreeding
Dr. Sawaya
- what did his study “prove”
- Scientist at Montana State University
- His 3 year long study proved that bears do want to cross the road [facilitating gene flow]
Crossing structures in Banff park
- a variety of over and underpasses that are designed to help animals cross the highway safely
- overpasses go around 50m-60m wide
- underpasses can be small or a large open underpass
what are other components of the highway mitigation system and what was its original intention?
fenced the sides of the highway to decrease the amount of roadkill
- originally intended to decrease wildlife deaths on the roads and improve safety on the road (for this purpose, rather than for the under/over passes)
INTENTION: IMPROVE PUBLIC SAFETY
how many crossings are on the highway
44
- during Sawaya’s study there were around 25
What may lead some people to not want to go through with the mitigation system
the cost; very expensive
- they also may not fully understand/misinterpret the intention behind the rationale behind the system
what species were studied
Black Bears and Grizzly Bears
- have different response to humans human infrastructure
—————-
Black Bears: less wary of humans, more likely to cross the road
Grizzly Bears: very wary of humans, less likely to cross the road
What can roads cause/create
Barrier Effects
- animals won’t cross the “barrier” due to behavioural avoidance
- due to the sights, sounds, or smells of the highway that make the bear unwilling to cross that area
- therefore putting in a crossing structure helps mitigate this risk and creates a safe way
How was the study done (techniques)?
1) sampling the crossing structures
- took strands of barb wire and strung it perpendicular to the line of movement
- allowed the scientists to collect the hair of animals [genetic data] who were crossing over or under the wire
- helped to identify the number of animals using the crossing: their sex, whether or not they were related, and whether or not they were breeding
(to put this data into context)
- 2 different methods were used to sample the population [involved hair collection to gather genetic data]
= powerful way to get a good handle on population characteristics and characterize the genetic structure
what did they find through the sampling methods
- ample amounts of migration, reproduction, and genetic admixture [gene flow]
- showing that crossing structures are working as intended to reduce the threat of genetic isolation
difference in results between grizzly and black bears
- difference has to do with historical effects {Trans-Canada highway has been around since the 40s, has had a greater effect on fragmenting the grizzly population}
- slight time lag, even though the animals have been using the crossover for years, only some population of grizzlies are beginning to reconnect now (because they’ve historically been avoidant of the road and have been fragmented for a longer time)
from the study: We detected a genetic discontinuity at the high-
way in grizzly bears but not in black bears.
number of grizzlies and black bears?
grizzlies: 113
black: 101
of the bears that were using these crossings, how did it break down demographically?
- number of males and females using the crossings
- identified that 47% of black bears had reproduced and 27% of grizzlies reproduced
- can’t get age out of DNA data alone atp, so they could only identify them as a breeder to identify adults
is the trans-canada highway compensating
- helps overcome the fragmentation caused by the highways
other animals?
- 140 000 crossings species
- garter snakes, moose, wolverines, etc.
- being used by a whole variety of species
success of these structures financially and biologically
win/win situation for humans and wildlife
- take care of one of our biggest threats to biodiversity
Busy
roads such as highways can act as barriers to animal movement through direct
mortality of dispersers or behavioural avoidance [2,3]. This can reduce access to
habitat and mates [1], and thereby reduce survival and breeding opportunities
In addition, when roads prevent migration between populations, genetic
diversity may be reduced and this will happen fastest in smaller, more isolated
populations
Climate change may be particularly harmful to fragmented
populations [6], because animals will be less able to move in response to chan-
ging environmental conditions, and because barriers may negatively impact the
evolutionary potential of populations, i.e. their ability to genetically adapt to
changing environmental conditions.
However, the deleterious effects of roads
may be minimized by wildlife crossing structures that may allow animals to
change movement patterns (i.e. latitude, elevation) in response to rising temp-
eratures and allow the flow of genes so that populations can adapt and evolve
to rapidly changing environments.
Fragmentation divides large populations into smaller populations that are
more prone to extinction owing to demographic and environmental stochasti-
city
Small, isolated populations also have less genetic diversity and are
more prone to extinction owing to inbreeding depression than larger, connected
populations [8– 10]. Genetic variation within a population can be lost because of
genetic drift following population fragmentation [11].
Small populations that
are isolated are more likely to experience inbreeding, because the probability
of identity by descent (i.e. identical copies of the same allele from a common
ancestor) increases faster than in larger populations. Small populations are
also more susceptible to disease epidemics and less able to cope with extreme
environmental conditions owing to a lack of genetic variation.
