150yearold map reveals that beaver dams can last centuries

first_img Click to view the privacy policy. Required fields are indicated by an asterisk (*) Now, that rare map is giving researchers some new insight into just how busy beavers can be. A new survey shows that many of the dams and ponds that Morgan saw nearly 150 years ago are still there—testament to the resilience of the rodents and their ability to maintain structures over many generations.“We haven’t known much about the long-term resilience of beaver populations, but this map allowed us to look back in time in a pretty unique way,” says ecologist Carol Johnston of South Dakota State University in Brookings, the author of the Wetlands study.Johnston learned of Lewis’s map while doing her postdoctoral work. She realized it was far older and more detailed than other records of beaver engineering; aerial photographs, for example, go back just about 75 years. And she wondered how Morgan’s dams and ponds had fared over the years, as trappers had wiped out many beaver populations, and people had built mines, roads, and homes.To find out, Johnston used an array of aerial imagery to create an up-to-date version of Morgan’s map, and then compared it with the original. She was surprised to see that, overall, 46, or 75%, of the original dams and ponds were still visible, although some appeared abandoned. And Johnston notes that although the animals, which live just a decade or so, may not have continuously occupied every dam for all of that time, “the remarkable consistency in … pond placement over the last 150 years is evidence of the beaver’s resilience.”“We’ve suspected that some beaver features can persist a very long time, but this is a very cool … way of quantifying it,” says wildlife biologist Christopher Pearl of the U.S. Geological Survey’s Forest and Rangeland Ecosystem Science Center in Corvallis, Oregon. Other studies, he notes, have suggested that beaver colonies can occupy an area for 1000 years.  Morgan reached a similar conclusion nearly 150 years ago, without the benefit of historical maps and aerial photos. In The American Beaver, he mused on the origins of some of the more impressive dams he saw, concluding that they must have been erected by generations of workers. “These dams have existed in the same places for hundreds and thousands of years,” he wrote, and “have been maintained by a system of continuous repairs.”Today, Johnston marvels at Morgan’s keen eye. “The guy,” she says, “was just a wonderful, wonderful observer.” Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe In the mid-1800s, a railroad director, entrepreneur, and politician named Lewis Henry Morgan began visiting a largely undeveloped swath of land dotted with beaver ponds in Michigan’s Upper Peninsula. What he saw amazed him: “[A] beaver district, more remarkable, perhaps, than any other of equal extent to be found in any part of North America,” he wrote. “A rare opportunity was thus offered to examine the works of the beaver, and to see him in his native wilds.”Morgan wasn’t your typical nature buff. His pioneering anthropological studies of Native American tribes had already begun to make him an enormously influential figure in 19th century science. In 1880, he would be elected president of AAAS (publisher of Science), and Charles Darwin, Sigmund Freud, and Karl Marx would come to cite his work. But as Morgan helped his railroad company lay tracks across the Michigan wilderness in the 1850s and 1860s, the target of his scientific curiosity was the North American beaver (Castor canadensis).For years, he carefully documented how the beavers behaved and where they built their dams and ponds. Then, in 1868, Morgan published his 396-page beaver bible: The American Beaver and His Works. Folded into each copy was a map, carefully drawn by his railroad’s engineers, which detailed the locations of 64 beaver dams and ponds spread over some 125 square kilometers near the community of Ishpeming.center_img Sign up for our daily newsletter Get more great content like this delivered right to you! Country Emaillast_img