Climate Disjunction: Impact on Altitudinal Migrators & Hibernators

[pattylou]

One of the changes that appears to be occurring in the North American climate, involves greater snow pack in the winters at high elevation, and warmer temperatures at low elevation.

This could have two important effects.

1) Animals that are migratory may find that environmental cues from one area to another have changed (more on this below).

2) The "average" temperature may appear fairly constant despite great changes at either end of the altitudes studied.

A report a few years back looked specifically at two species. One, a marmot, hibernates at low elevation and moves to higher elevations after coming out from hibernation. The second species, a robin, flies to higher elevations when certain environmental cues stimulates such behavior.

Both species are migrating earlier and earlier, as low altitude climate warms. This creates a probelm, however, because the thicker snowpack prevents these species from finding food at the higher altitudes. Here is the abstract of the article:

Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years. This result differs from growing evidence from low altitudes that climate change is resulting in a longer growing season, earlier migrations, and earlier reproduction in a variety of taxa. At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, perhaps because of the trend for increased winter precipitation. This disjunction between phenology at low and high altitudes may create problems for species, such as many birds, that migrate over altitudinal gradients. We present data indicating that this already may be true for American robins, which are arriving 14 days earlier than they did in 1981; the interval between arrival date and the first date of bare ground has grown by 18 days. We also report evidence for an effect of climate change on hibernation behavior; yellow-bellied marmots are emerging 38 days earlier than 23 years ago, apparently in response to warmer spring air temperatures. Migrants and hibernators may experience problems as a consequence of these changes in phenology, which may be exacerbated if climate models are correct in their predictions of increased winter snowfall in our study area. The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover also have implications for hibernating species.


The reference is:

PNAS Vol. 97, Issue 4, 1630-1633, February 15, 2000 Climate change is affecting altitudinal migrants and hibernating species David W. Inouye, Billy Barr, Kenneth B. Armitage, and Brian D. Inouye

Note that these species are migrating weeks ahead of schedule. Note also that the increased snowpack has left the "melt date" largely unchanged at high altitudes, and note that this is particularly problematic for animals that have evolved with a certain synchronization of micro-environments.

 

[iansmith]

Going along with climate change and its influence on animal behavior, this might be of interrest: http://www.nrs.mcgill.ca/humphries/documents/ICB2004.pdf

There also people looking at the influence of climate change on mating behavior in Yukon squirrel.

Squirrels show genetic responses to warming: Canadian Study. Feb. 12, 2003. CBC News.
For the first time, scientists believe they have found an instance of climate change causing a species to alter its genetic makeup -- not just its behavior. To date, species changes stemming from climate change have all been behavioral, such as animals shifting their migration patterns. But after studying the DNA and mating habits of red squirrels in the Yukon for 10 years, scientists at the University of Alberta, Canada, have found that the squirrels give birth three weeks earlier in the year, corresponding to the earlier arrival of spring. More important, the scientists found that the change is partially genetic in origin -- that squirrels access to food and territory, then pass on their early-breeding preferences to the next generation.

http://www.uni.edu/ceee/eii/resource.shtml

 

[Andre]

It might be an idea to correlate those date changes with the local climate changes. This is a most excellent place to do that.

http://data.giss.nasa.gov/gistemp/station_data/

Colorado Rockies. So I clicked in that area and the closed station coming up is Telluride

http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=425745210060&data_set=1&num_neighbors=1

Now indeed we see a distinct warming after 1980 preceeded by an even more distinct cooling after the fifties. Try some other stations, you will see large differences in temperature behavior. I'd expect biota to react on that.

 

[pattylou]

...you will see large differences in temperature behavior. I'd expect biota to react on that.

Indeed. We do expect biota to react to climate. Likewise, the reaction of biota can indicate that environmental conditions have changed.

 

[Moonbear]

This is interesting. I wouldn't have expected temperature to have such a profound effect. Typically, it's believed that photoperiod is the major time cue for seasonal behaviors in birds and hibernating mammals and that temperature is a fairly minor contributor. Well, actually, hibernation itself can be temperature dependent, but the reproductive function shouldn't be (there's a large body of literature on this).

Alternatively, the proximate cue for seasonal behaviors is nutrition. Perhaps the changing temperatures aren't being directly perceived by the animals, but indirectly via the foods they are eating. If warmer ground temperatures lead to earlier sprouting of spring plants, I can't recall what species it is, but there's evidence that at least some animal species enter the breeding season as a result of eating plants rich in estrogenic compounds that only emerge in early spring.

It seems it's time to revisit the role of temperature in timing of seasonal behaviors in these species believed to be predominantly photoperiodic. The old studies ruling out temperature effects primarily focused on clamping temperature as a constant and varying photoperiod and showing that seasonal changes still occurred in reproduction. They may have also varied temperature with a constant photoperiod. But, there's some evidence that temperature might fine tune the onset of the breeding season once an appropriate photoperiod is reached. This isn't really focused on in current literature, but it may be what's going on here in slightly advancing the breeding season of these species. If that's the case, there ought to be a limit to how much drift there can be from the time of the optimal photoperiod conditions. Nonetheless, it makes it more relevant to study if that's what's going on here.

Sorry for a lack of references here. This is stuff I've read ages ago, and some of the studies will probably be too old to find anything more than an abstract online. I can try to dig up some of them, though I wouldn't have anything specifically on robins or marmosets anyway, which are the relevant species here (and they might just be a bit different from the species that have been studied in this sort of context).

 

[pattylou]

I remember photoperiod for blooming, but never learned how universal such a phenomenon is. There are two species of plants that compete in the open spaces here. One germinates based on light (the lupines, a legume) and one germinates based on temperature (members of the grass family.) At least, this is what I have been told.

As spring temperatures warm earlier, but do not experience longer days earlier, the grasses germinate earlier and outcompete the lupines. At least this is the idea I have heard for these two plant types.

 

[Andre]

So in the Netherlands there is a big experiment about the spring firsts, first eggs, first young, first return from seasonal migration, etc. And sure enough, everything gets earlier. So, if a only a handfull of biologists was registating this originally and now large parts of the population are helping, what would be the change in difference between the actual (but unnoticed) first and the observed first?

So a definite bias risk by changing observation methods. Hence observations about those temp vs photoperiod reaction should be strictly controlled.

About the opening study,

American robins, which are arriving 14 days earlier than they did in 1981

Would there also be data of say the 1950 era, when the average temperature in the west USA was about the same as nowadays?

 

[pattylou]

So, if a only a handfull of biologists was registating this originally and now large parts of the population are helping, what would be the change in difference between the actual (but unnoticed) first and the observed first?

You lost me there --- But do you realize that Moonbear's photoperiod comment (and my own) are from hazy recollection and may not accurately reflect what biologists working on such things, have demonstrated?

Would there also be data of say the 1950 era, when the average temperature in the west USA was about the same as nowadays?

We'd like to see such data, certainly, for this thread. If you find it, please let me know.

What I *do* know is that marmots are threatened. THis would be consistent with the idea that they are competing less and less well, and perhaps in part because of climate disjunction.

 

[iansmith]

Would there also be data of say the 1950 era, when the average temperature in the west USA was about the same as nowadays?

If the birds are migrating, the temperature from the point origin might given better insight. The environmental queue is probably from the point of orign rather than the point of arrival.