This week I take a look at a little known Alberta claim to fame. It’s the only place on Earth, outside of the Arctic and Antarctic, to successfully keep out the most destructive pest on the planet – the Norway rat.
I also look at a story out of Yellowstone National Park where the introduction of non-native trout 100 years ago, has created an ecological disaster in Yellowstone Lake…and with that said, let’s get to it.
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Keeping Alberta Rat Free
Alberta is a special place. We have amazing mountain landscapes, rolling prairies, fields of golden wheat, and yellow canola. Yet despite all of the things we have, Alberta is also special for one thing it lacks: the Norway rat.
For most visitors to this landlocked province, the idea that any place, no matter how remote, could be free of these devastating rodents is almost incomprehensible. Rats are one of the most adaptable animals and they continue to plague humanity anywhere in the world people visit, rats hitch a ride and move in. That is everywhere but Alberta.
Norway rats were responsible for the Bubonic Plague, or Black Death that spread through Europe between 1347 and 1351. Rats are hosts to tiny fleas that, in turn, transmit the disease to humans. They also spread diseases like hepatitis, tularemia, hantavirus, leptospirosis, and even typhus.
When rats invade new territory, they spread incredibly fast. According to the Alberta Invasive Species Council:
“Norway rats are non-native species that spread and reproduce at a rapid rate because females can produce offspring every 21-23 days in litters of up to 12 young. In one year a female rat can have up to 15,000 offspring. “
It only takes a few rats to b uild a resident population and once they’re established, it becomes almost impossible to eradicate them – just look at the rest of the world. In every case where rats colonized a new territory, they were there to stay.
The first Norway rats arrived with ships along the east coast in or around 1775. From there they spread westward at alarming rates. As settlements moved westward and farms replaced prairie grasslands, the rats followed.
Wherever people live, save the Arctic and Antarctic, rats are happy to pick at our scraps. Like all rodents, they also need to gnaw to keep their teeth trimmed. They can easily destroy buildings and other structures through their constant chewing.
According to a Government of Alberta article on the History of Rat Control in Alberta:
“Rats entered eastern Saskatchewan in the 1920s and extended their range to the northwest at about 24 km (15 mi) per year. Rats were first reported on the eastern border of Alberta in 1950, and would have continued to spread westward had it not been for a rat control program that halted their advance and continues to maintain an essentially rat-free province to date.”
When the first rats were discovered on the Alberta border, in Alsask, the government of Alberta decided to act quickly to keep them from spreading. It was this early decisive action to prevent rats from getting established that has kept the province rat-free to this day.
The responsibility for rat control was given to the Department of Agriculture and there was already legislation from 1942 called the Agricultural Pests Act of Alberta. It gave the Minister the ability to designate any animal as a pest if it threatened Alberta’s farms. It also made it the duty of every citizen to work to destroy any designated pest animals.
Almost immediately, the legislation required every municipality to designate a pest control inspector. Today’s rat control program can be traced back to William Lobay, who came up with the idea of a rat exclusion zone designed to keep rats out of the province. He created and managed the program between 1950 and 1953.
The first step was education. Albertans needed to know just how destructive rats are and why they needed to keep them from getting a foothold in the province.
Educational programs began in earnest and several conferences were held in the province. By 1952, 30 rat infestations had occurred along 180 km of the Alberta-Saskatchewan border. Within a year, rats were being found along 270 km of the border.
The government hired private extermination firms at first until they could develop their own program. The weapon of choice at the time was arsenic. According to the Alberta website:
“During June 1952 to July 1953, some 63,600 kg of 73 percent arsenic trioxide tracking powder was used to treat 8,000 buildings on 2,700 farms (24 kg/farm; 8 kg/building) in an area 20 to 50 km wide and 300 km long between Medicine Hat and Provost.” The document continues
“Tracking powder was blown underneath all permanent buildings within the control zone. While only permanent buildings were supposed to have been treated, some temporary structures were treated as well.”
People living in those buildings had to be educated about the dangers of these poisons and while expensive, the program was very effective and continued until 1978 when it was deemed too expensive.
By 1959, the program still being used today was in place. Each community appoints pest control inspectors and they’re responsible for preventing incursions into the province. Each inspector was responsible for the following tasks:
- “check every premise within the first three ranges (29 km) west of the border
- distributed bait and established bait stations
- encouraged rat-proofing of buildings and the removal of rat harborage and food
- destroyed any rat infestations that were found”
Today, warfarin, a commonly used blood thinner, is used as the main source of rat poison.
It took 10 years for the rat control program to really show progress. The 1950s were characterized by public education, gaining experience on how to eradicate infestations, and essentially getting the public to buy-in to the program.
Rats still show up in Alberta. the numbers of infestations vary from a few dozen to a few hundred every year, and they’re quickly dealt with. White lab rats and domestic rats are also prohibited and must be reported. They can just as easily start an infestation as the more well-known Norway rat. So keep in mind that if you have a pet rat, you better not bring it to Alberta. They are strictly prohibited.
Today, Alberta spends around half a million dollars per year on its rat control program. It’s likely one of the best investments they could ever make. It is estimated to save them $42 million a year in potential economic and environmental damage if rats were to get established in the province.
It’s remarkable to look at a rat range map of the world and to see one Alberta-sized hole in it. It’s a credit to the province that their rat control program has managed to do what no other jurisdiction on the planet has accomplished. While the methods used to keep Norway rats out of the province are extreme, the implications of not doing it would be much more destructive.
Keep in mind that the bushy-tailed woodrat (or pack rat), is not on the list of prohibited rats. It’s a native species that is a common resident in many of the caves in the area. They can be a pest if they move into your house, but generally, they’re harmless. Just don’t leave any wool clothing near caves or it may get incorporated into their nest.
Other invaders are on the way
As climates change, the province will likely see many other species begin to move in. Plants and animals are moving north with warming temperatures.
Animals like raccoons are now being reported in many parts of the province. Historically limited to the southeast corner of Alberta, they’re on the move and have expanded to central Alberta.
Bobcats are increasingly common in places like Calgary and, like coyotes, are very happy to hang out in urban areas. They are quickly becoming established in areas further and further north as climates warm.
White-tail deer have been rapidly expanding their range over the past 50 years as temperatures increased and opened new territories for them. In the Rockies, this was traditionally mule deer country, but increasingly we’re seeing more and more white-tail moving in.
How Introduced Lake Trout are Causing an Ecosystem to Collapse in Yellowstone
Since Yellowstone National Park reintroduced the gray wolf in 1995, it has been seen as an example of how ecosystems can be rehabilitated. It showed that reintroducing a keystone species like wolves could bring positive changes that ripple throughout the entire ecosystem. Back in episode 45, I looked at how the reintroduction of wolves into Yellowstone had very positive impacts that spread across the ecosystem.
Unfortunately, there is another story playing out in Yellowstone at the moment that shows the polar opposite of the wolf reintroduction. It shows that introducing the wrong species, in this case, lake trout, can cause a functioning ecosystem to virtually collapse.
I’ve spoken at length in previous episodes how integrated living systems are, and how pulling on one thread can ripple throughout the entire ecosystem. Here in the Rockies, we can look at a simple three pillar relationship between wolves, coyotes, and fox. When wolves are the top dog, as they are in many ecosystems, they keep coyote numbers down.
Coyotes compete with them for some foods, but also scavenge their kills. Red fox, on the other hand, doesn’t directly compete with wolves and so they are left alone. In a wolfy landscape, you tend to see a triad of strong populations of wolf, coyote, and fox.
Take away the wolf, and the coyote becomes the top predator. They, in turn, displace fox. In the past 35 years, I’ve seen 4 foxes in the mountain national parks – all of them within the last 5 years. As wolves have reclaimed their dominance, they have reduced coyote numbers. This, in turn, has allowed the fox to move back into territories long vacated.
While this may seem like a simplistic example, it has deep implications on the ecosystem. If you want to know how deep, check out episode 57.
Recently, news has come out of Yellowstone that all is not well. There are ecological interactions taking place that are wreaking havoc on the sensitive aquatic ecosystem around Yellowstone Lake.
Just like the wolf reintroduction showed the benefits of bringing back species essential to a landscape, adding ones foreign can have effects that also cascade through the entire system.
The ecosystem around Yellowstone Lake is a story 10,000 years in the making. As glaciers receded at the end of the Ice Age, life returned to places it had previously been limited by glacial ice.
Often, its the smallest creatures that are the first to colonize a landscape, and they often first colonize the water, creatures like phytoplankton. The word phytoplankton comes from the Greek words meaning “drifting plant”. They are tiny algae and diatoms that take advantage of sunlight to convert the sun’s energy into sugar. They’re powered by chlorophyll, the same substance that turns land-based plants green.
Phytoplankton is responsible for around half of the photosynthesis on the planet and forms the foundation of many aquatic ecosystems. As they absorb the sun’s energy during photosynthesis, they release oxygen into the water. By some estimates, these tiny algae produce between 50% and 80% of the planet’s oxygen. The rest is produced by photosynthesis of land-based plants.
As it turns out, phytoplankton is tasty and nutritious, for creatures specialized in feeding on them. Tiny copepods, only 1 or 2 mm long, love phytoplankton. These tiny crustaceans are incredibly varied in appearance, but they usually have an elongated body with oar-like arms that help them move through the water.
Along with the copepods are slightly larger crustaceans commonly called water fleas. Ranging in size from 0.2 to 6 mm, they’ve been a key part of aquatic food chains for the past 33 million years or so. These rugged creatures can reproduce with or without a partner. While asexual reproduction is the rule, occasional mating helps produce eggs that can help them survive harsh climatic conditions like droughts.
These three groups of animals form the foundations of the ecosystem in Yellowstone Lake. Life in this lake, like many northern lakes, is not easy. It’s frozen for around 5 months every year, and it’s deep and cold.
As far as nutrients go, it isn’t bad, and it also has good oxygen levels. Overall, it’s a good place for phytoplankton, Copepods, and water fleas to thrive.
Insect larvae and amphipods, or freshwater shrimp as they are often called, round out the foundation. These tiny crustaceans, usually less than 1 cm in length are another critical aspect of most freshwater ecosystems.
Ok, the stage is set, or should I say the buffet. Once you have a foundation for a food chain, it’s time to bring on the stars.
At some point in the 10 millennia since the glaciers melted, cutthroat trout managed to migrate across the continental divide at Two Oceans Pass and make their way into Yellowstone Lake.
The landscapes surrounding Yellowstone Lake are also perfect for cutthroat trout – especially since for perhaps several millennia, they ruled this high-elevation lake. They were the only fish species able to make their way over the Continental Divide to get to the lake and subsequently thrived here.
They spend their lives in the shallower parts of the lake, usually in waters less than 20 metres deep. With the spring melt, it’s time for them to spawn forcing them to leave the lake, swimming upstream into some 60 tributary rivers draining into Yellowstone Lake.
This combination of spending their lives in the shallows of the lake and then heading into shallow streams makes them prime pickings for a diversity of animals and birds looking for a meal.
Grizzly and black bears timed their annual foraging around this easy source of protein as the trout sought out shallow, easily fishable channels, in order to lay their eggs. Osprey and bald eagles thrived. River otters, white pelicans, loons, all found a plentiful food supply…and since the trout had no competition, they reproduced in huge numbers ensuring there was always trout for hungry predators. In all, there are 4 types of animals and 16 different bird species that have cutthroat trout on their menu.
When a single species is a key food source for so many animals, anything that disrupts this conveyor belt of protein and nutrients creates impacts that ripple throughout the entire ecosystem. If some 20 animal and bird species find themselves without a critical food source, it creates impacts that spread throughout the food chain…enter lake trout.
Today, park managers look at landscapes in a very different way as compared to decades ago. Where today, ecological integrity is the mantra and each link in the chain is seen as an integral domino that mustn’t be tipped over, this wasn’t the case in the early days of many parks.
In 1872, most of Yellowstone National Park’s many lakes and streams were fishless. Since the ice had receded, there was simply no way for fish to get to the area because waterfalls prevented migrations. To early park managers, in a time where parks were seen as a place to be civilized, no fish simply meant empty.
It was never considered that the lack of fish was not a lack of life. Just because fish had not naturally made their way to these parts of the Yellowstone ecosystem did not mean the lakes and streams were not productive. Current ideas about conservation and ecology were still a generation away.
Neither did these early land managers look at the few lakes that DID have fish, like Yellowstone Lake with its cutthroat trout, and consider whether they might be better a better choice for any planned stocking program. After all, if you want to stock lakes with fish, why not use a species that is already a part of the existing ecosystem, and which is already a critical part of the food chain?
Ecosystems were simply not a thing back then. Wilderness was seen as a place to be utilized and made attractive to potential tourists. Who wouldn’t want to go on a fishing trip?
In 1890, park managers thought they would help out and they brought a few lake trout from Lake Michigan. What could go wrong? just a few lake trout in Lewis and Shoshone Lakes. Sometimes it’s the simple things. The one decision that ripples through a landscape…and this is the one that changed Yellowstone.
A few fish might seem like not a big deal, but fish colonize, reproduce, and eventually need to disperse…and disperse they did.
They outgrew these original lakes and expanded to Heart and Jackson Lakes and, after 100 years of slow expansion, they were first discovered in Yellowstone Lake in 1994.
Yellowstone Lake was perfect for lake trout. It’s deep and cold, exactly what they are built for. It took only a few, and they made two friends, and they made two friends. However by 1994, the old attitudes were gone, ecological integrity was de rigeur, and wolves were about to be reintroduced to the park.
Officials realized that lake trout might have a negative impact on the ecosystem and so they began a program of gillnetting in an attempt to eliminate them from the lake. They gillnetted and gillnetted. By 1998, they estimated a population of 125,000 fish older than 2 years. By 2012, the number had ballooned to 790,000. During the intervening period, they had also removed 800,000 fish through netting programs. Netting has since been dramatically increased as the impacts of this invasive species spreads.
Lake trout are pretty flexible feeders. The eat zooplankton, insect larvae, small crustaceans like water fleas and freshwater shrimp, clams, and also small fish like the native cutthroat trout.
How many fish can lake trout eat? In 1998, it was estimated that the 125,000 lake trout estimated to be in the lake would have chomped down 3-4 million cutthroat trout in that single year. Take a moment to ponder that. That’s 3-4 million fish that are no longer present in the ecosystem. They’re no longer available to eagles and osprey as they hunt on the lake. They aren’t spawning upstream from the lake where black and grizzly bears, along with river otters could feed on them.
As lake trout gobbled down cutthroat trout, impacts on the landscape quickly became evident. During the netting programs in Yellowstone, some cutthroat trout were also caught. In 1987, around 50 cutthroats were caught per unit of netting. At the same time, they were equally represented by all sizes showing a healthy population. By 2010, only 13 were seen in the same netting unit and fewer and fewer young fish were encountered.
As lake trout continued to feast on young cutthroat, the effects immediately rippled through the ecosystem.
As cutthroat trout numbers diminished, but the impacts began rippling in both directions in the food chain. Cutthroats preferred to eat the larger water fleas, leaving more of the smaller copepods in the aquatic ecosystem. In fact, water fleas represented 80% of their diet in 1989 but had dropped to 11% by 2011 due to competition with the more aggressive lake trout.
This forced them to feed more heavily on freshwater shrimp, which ballooned from 8% of their diet in 1989 to 79% in 2011. This seemingly simple change meant that the entire aquatic mix of algae, copepods, water fleas, and freshwater shrimp also changed. Instead of water fleas being most prevalent, the smaller copepods began to dominate. The lake began to reflect this lack of aquatic diversity as the water began to appear clearer and clearer…and clear water is not always a sign of a productive body of water.
Then the impacts radiated outward from the lake. Yellowstone Lake is like a heart at the centre of a circulatory system. Into this heart drain dozens of tributary rivers which form the spawning grounds for cutthroats. They abandon the lake for several months each spring during the spawning season. For local bears and otters, it’s like a buffet radiating upstream as well.
Trout that were previously available only to osprey, eagles, loons, and a few other lake feeding anglers, were suddenly available to many other animals and birds.
Black and grizzly bears, along with river otters took great advantage of this bounty and spent considerable time plucking cutthroat trout from their shallow spawning beds.
As populations dropped in Yellowstone Lake, fewer and fewer trout ventured into the rivers to spawn.
(Above) Watch a short National Geographic video that illustrated cutthroat trout spawning in Yellowstone National Park. The whole music thing is a bit creepy, but the science is sound.
As tributary cutthroat numbers dropped, so did the number of black and grizzly bears wandering the river banks. In the mid-’90s, grizzlies were active on 93% of the tributaries, and active feeding was found on 61%. In 2008, 2009, and 2011, not a single bear was found feeding. It wasn’t worth the effort for the few fish available to bears anymore. Grizzly bears switched tactics and began to focus their hunting efforts more towards elk calves and away from the rivers.
In just one decade, the number of bears feeding on tributaries dropped by 63%., and the number of black bears was reduced even more.
Estimates in the late 1980s had grizzlies eating almost 21,000 fish annually, but that number dropped 10-fold to just 2,266 by the late 1990s and just 302 by the late 2000s.
River otters were also impacted. The tributary streams radiating out of Yellowstone Lake are ideal for these aquatic weasels. While they are incredibly agile in the water, they don’t travel far overland. The rivers are their buffets. During the years of 2002-03, trout remains were found in 72% of otter scat collected at 87 sites.
Ok, time for an important message here…scat is not just crap…it’s nutrients. Otters, like other members of the weasel family, don’t look at poop as just, well poop. It’s a billboard announcing one weasel to all of the others in the area.
Otters, take this to another level. They create communal latrines that become a social hub, particularly between male otters. To male otters, a latrine is a gathering place where they get to know each other, decide who to hang out with, and plan their otterly social game.
Weasels like to present their excrement in prominent locations. While cats spray and bear rub and scratch, weasels poop. Most days hiking in the mountains, I’ll pass a prominent rock with a poop that looks like some twisted rope. That’s usually a weasel marking its territory.
This video, while pixellated and poor in quality, shows how social otters are in their latrine habits.
Every otter that visits the latrine contributes to nitrogen and other nutrients to the local landscape. As the number of otters drops, so do the nutrients.
Birds, more than any of the larger mammals, relied heavily on cutthroat trout. Some of the impacts are difficult to determine since many birds of prey, in particular, bald eagles and osprey, were decimated during the DDT years. This makes it harder to build an accurate historical context for these birds.
During the peak of DDT usage, there were generally 4-6 eagle nests on Yellowstone Lake. The number increased to 16 between 1987 and 2003 but dropped to 12 nests by 2007. However, the number of nests doesn’t represent the success of those nests. The only point of nesting is to successfully raise young.
in the 80s, while hair bands were screaming on the radio, eagles were successfully fledging 60-80% of their nestlings. By 2009, that percentage had dropped to zero!
As cutthroat trout became more scarce, eagles simply changed their tactics and began to hunt other prey. Unfortunately for the many waterfowl around Yellowstone Lake, they now were placed squarely on the menu.
Eagles began to focus on California gulls, American white pelicans, double-crested cormorants, and Caspian terns. Even loons were taken on occasion.
In 1990, according to biologist Doug Smith, 28 pairs of Caspian terns nested on the Molly Islands, but they all disappeared by 2005. There also hasn’t been any successful rearing of California gulls.
Loon populations have dropped by 50% since 1990. Higher spring snowmelts leave nest sites flooded out, the number of cutthroat trout available to hunt has dropped precipitously, and now eagles actively look at loons for dinner.
On another lake, Riddle Lake, eagles have hunted rare trumpeter swans. By 2011, only 5 swans were left in the park. Efforts to restore them have helped their numbers increase so there are now around 25 swans in the park. Unfortunately, they don’t seem to be successfully raising any young.
At the same time, the aggressive netting of lake trout also benefited the eagles and cutthroat trout began a slow recovery.
Osprey once thrived on Yellowstone Lake. For a bird that eats exclusively fish it catches talons first, a lake resplendent with shallow-water trout was a perfect buffet. Their numbers plummeted from 60 nests in 2001 to just 3-5 between 2008-2015. As smaller trout disappeared from their hunting grounds, they moved to other lakes. Unlike eagles which are flexible in their hunting habits, osprey hunts only one prey – fish. They simply abandoned the Yellowstone Lake ecosystem.
Doug Smith, Yellowstone’s project leader on the gray wolf reintroduction project, but also an expert on the other aspects of the ecosystem has been raising alarm as he sees a major ecosystem collapse taking place in the park.
Smith began to notice an increase in large waterfowl mortality. He saw a few feathers here and there but didn’t connect the dots. He quickly realized that eagles had switched from hunting the now unavailable cutthroat trout to other waterfowl.
Suddenly, the entire avian spectrum found itself on the eagle’s menu. They’re hunting everything from loons, California gulls, Caspian terns, and even white pelicans now that their preferred foods are less available to them.
While in the summer of 1997, there were 67 young ospreys that fledged, there were just 3 nests in 2017 and only a single nestling fledged. In the early 90s, there were 16 species of birds feeding on fish in Yellowstone Lake.
While osprey abandoned the area, eagles turned their talons elsewhere…in particular to other birds. Suddenly the lake’s populations of California gulls, American white pelicans, double-crested cormorants, and Caspian terns were all on the menu. Every one of these species has been decimated.
Park officials have known for a long time what they needed to do, but it is nearly impossible…They need to exterminate the lake trout. As long as these deep water hunters are killing young cutthroat trout, it will continue to impact the balance of foods available across the ecosystem.
While park managers agree that the lake trout have to go. Unfortunately, it’s not that easy. As fishing efforts have gotten more aggressive over the past decade, cutthroat stocks are beginning to rebound. Unfortunately, it will be nearly impossible to eradicate the invasive lake trout. Gillnetting programs will need to continue indefinitely in order to allow cutthroat trout to survive, and to continue to contribute to the overall ecosystem.
All it took was just one fish…one fish that doesn’t belong in this landscape.