Photo by D. Sillman
I was reading a paper a few days ago about some of the potential impacts of a warming climate on the hardwood forests of eastern North America when I came to the following sentences:
“…. you have to look at things like competition. Young trees rely heavily on the shoulder seasons — spring and fall — to grab the light they need.”
Shoulder seasons? New terms are always popping up, but they usually have some obvious roots or contexts. Who calls the spring and fall the “shoulder seasons?” I took to Google to find out!
The travel and tourism industry, apparently, regularly uses this phase to identify the times in between the peaks and the lulls of travel. If you imagine an X-Y graph with a Y-axis representing hotel reservations made at some seaside resort or plane tickets bought to travel there, and an X-axis that represents the months of the year, you could visualize large numbers of visits and flights in the summer and some very low values in the winter. Connecting these peaks and lulls is the sloping rise or fall that represented the transitional seasons. Slopes that could be called the “shoulders” of the graph!
Backpacking uses the term “shoulder season” for the early spring and late fall, times when winter is lingering or coming on sometimes astonishingly quickly. The shoulder season is a good time to find open trails and empty camps (and maybe a foot of snow on your tent when you wake up in the morning!).
The term is also used by people who burn wood for heat or cut logs for firewood. It has been also been used to describe the timing of particular hunting seasons (like the ‘elk shoulder seasons” in Montana). Gardeners use the term to talk about squeezing in a quick crop of beans or squash before winter slams the door on plant growth. A Lutheran minister talks about the “shoulder times” just before Christmas as the ideal time for true religious contemplation. There are also all sorts of clothes and fashion accessories all focused on this very interesting time (and term!).
I don’t what I would have thought if I had come across Montana’s “elk shoulder season” before I had explored this word. I think I would have envisioned images of gruesome carnage in the mountains with shoulderless elk carcasses strewn across the countryside and discrete racks of elk meat grilling over camp fires.
Photo by Rachel J., Pixabay
Speaking of elk: there was a paper published this past summer (PLOS ONE, June 14, 2017) that explored the survival behaviors of a herd of elk in southwestern Canada. Human hunters are the primary predators of these elk, and because of hunting regulations and trophy considerations the male elk (“bulls”) are the herd component that is preferentially hunted and killed. Males are also easier to hunt because they can be actually drawn to hunters because they respond so predictably to the mimicked bugling calls of potential competitors. It is not surprising, then, that bulls of this herd typically only live to five years of age.
Female elk (“cows”) are also hunted although somewhat less intensely. Cows can live up to twenty years and hunting censuses have noted that cows older than ten years of age are almost never taken by hunters! Researchers at the University of Alberta wanted to explore the reasons for this remarkable survival rate of these older cows. Did they survive because they simply had been born very careful and cautious and remained so all of their lives (a “nature” explanation)? Or had they developed increasingly effective survival skills through their long lives through learned interactions with potential hunting experiences (a “nurture” explanation)?
Photo by T. Hisgett, Wikimedia Commons
The researchers, intensively monitoring the movement of forty-nine cows over periods of two to five years with GPS collars, found that both explanations were appropriate. Cows begin life with a higher level of caution than bulls and are thus genetically able to more effectively avoid hunters (and, logically, other potential predators, too). This innate level of caution, though, becomes more developed as the cow ages. Older cows move shorter and shorter distances during the day, and they seek rougher, more remote terrain, and actively avoid roads and other human impacted landscape features. Any experience involving human hunter contact quickly leads to a particular cow avoiding that terrain or locale in the future. Cows also tend to live in small groups and are able to share their hunting avoidance experiences and thus expand the entire group’s overall survival strategies.
So, these elk cows because of innate caution and a high level and quality of learned (and shared) experiences, become almost invulnerable to hunters. They are able to live and reproduce well into their second decades of existence.
Photo by F. Dunn, Flickr
And finally, in Morocco a historically hot and dry climate that has become even hotter and drier under the influence of ongoing climate change. Moroccan goats, a very abundant domesticated animal that has for millennia scrambled agilely over the rocky hillsides to glean and gather plant materials for their food, now face many months of the year where there are no food materials to be found among the rocks. These goats in response to this food deprivational stress have developed new behaviors that enable them to survive in their changed world. They have learned to climb the scattered argan trees! Up in the branches of these trees the goats graze on both leaves and the nut-like seeds. The human, goatherds actually prune the lower tree branches to help the goats make the leap from the ground into the trees! In the autumn, the height of the dry season in Morocco, few goats are seen on the rocky hillsides! Instead, in scenes that evoke illustrations from Dr. Seuss, the goats are all up in the trees!
As Michael Creighton wrote in his novel Jurassic Park, life will find a way!