Topic Results: Beaver History

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Human-beaver cohabitation in the Early and Mid-Holocene of Northern Europe

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For thousands of years, beavers had a big influence on the Dutch ecosystem and the people that lived there. This is the conclusion of research by archaeologist Nathalie Brusgaard. The rodents were used for food, clothing and tools, and created a landscape hospitable to many other species.

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Prescott Peninsula Beaver Survey Results – 2017

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There were 7 active beaver colonies (7 interior and 0 along the shoreline) documented on the Prescott Peninsula during the 2017 survey. This relatively low count of 7 was also recorded in 1960 and 1993. A downward trend has continued from a total of 23 active colonies in 2013 to 7 in 2017. There were 6 interior survey routes that were active in 2016 and still  active this year, along with 1 re-colonized site. Detailed locations are provided in Table 1. Locations of active sites are shown in Figure 1. Long-term population trends for beaver on the Prescott Peninsula over the last 50+ years are summarized in Figure 2.
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Prescott Peninsula Beaver Survey Results – 2021

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There were 12 active sites documented on the Prescott Peninsula during the 2021 survey; 10 were within interior routes (26% occupation rate) and 2 found along the shoreline. Two active sites were recorded along one of the interior routes. The remaining active routes had one
active site. One shoreline site was found on the western side of the peninsula and the second tucked in Prescott Cove on the eastern side of the peninsula. In 2020 there were 14 active beaver sites within the interior routes, and one found along the shoreline. Eight of the same survey routes had active beaver sites in both 2020 and 2021. There was one re-colonized route in 2021 (i.e., not active in 2020 but active in 2021). The 20-year average is 14 (36% occupation rate) for number of active beaver sites within the interior routes. Active beaver lodges along the peninsula shoreline have ranged from 0 in 1952 when the surveys began, to a high of 17 in  1974. However, over the years since, the number of active lodges along the shoreline has continued to decline, with an average of 2 active sites for the past 20 years. Locations of active sites are shown in Figure 1. Long-term population trends for beaver on the Prescott Peninsula over the last 50+ years are summarized in Figure 2.
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Prescott Peninsula Beaver Survey Results – 2022

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There were 13 active sites documented on the Prescott Peninsula during the 2022 survey; 12 were within interior routes (31% occupation rate) and 1 found along the shoreline. Two of the interior routes each had two active sites. The remaining active routes had one active site. The shoreline site was found on the eastern side of the peninsula. In 2021 there were 10 active beaver sites within the interior routes, and two found along the shoreline. Six of the same survey routes had active beaver sites in both 2021 and 2022. There were four re-colonized routes in 2022 (i.e., not active in 2021 but active in 2022). The 20-year average is 13 (33% occupation rate) for number of active beaver sites within the interior routes. Active beaver lodges along the peninsula shoreline have ranged from 0 in 1952 when the surveys began, to a high of 17 in  1974. However, over the years since, the number of active lodges along the shoreline has continued to decline, with an average of 2 active sites for the past 20 years. Locations of active sites are shown in Figure 1. Long-term population trends for beaver on the Prescott Peninsula over the last 50+ years are summarized in Figure 2.
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The oldest semi-aquatic beaver in the world and a new hypothesis for the evolution of locomotion in Castoridae

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The North American rodent fossil record includes hundreds of species representing both an incredible taxonomic diversity and great ecological disparity. Although it is during the Oligocene that taxonomic diversity first peaks, it is not until the Miocene, almost 10 Myr later, that many ecologies, particularly locomotory ecologies, are recorded. Here, I present a new Oligocene-aged species of beaver from Montana, Microtheriomys articulaquaticus sp. nov., which represents the oldest semi-aquatic rodent in North America and the oldest amphibious beaver in the world, pushing the advent of semi-aquatic ecology in beavers by 7 Myr. I also provide morphological data supporting a terrestrial ecology for the sister taxon to Castoridae. Together with existing data, these findings lead to a new hypothesis for the evolutionary ecology of castorids whereby swimming was exapted from burrowing during the Oligocene. This evolution of semi-aquatic locomotion may have taken place in North America instead of Eurasia. It started in small beavers with gigantism achieved only much later. Indeed, body size evolution in castoroids follows a directional drift. Beavers obey Cope’s rule, a selection for larger size over time that appears associated with semi-aquatic ecology and may well explain their low modern diversity.

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