Study finds small mammals aid expansion of warm-climate trees

JULY 19, 2019

by University of Maine

A new study by Alessio Mortelliti, an assistant professor of wildlife habitat ecology at the University of Maine, finds small mammals could affect whether trees spread to new areas in a warming climate.

Mortelliti's research, which was published in the journal Oikos, looks at the behavior of small forest mammals that eat acorns and other tree seeds.

By choosing certain seeds and rejecting others, the animals can alter the trees that make up a forest, according to a Second Century Stewardship news release.

If they eat all the seeds in their territory, those seeds can't grow into new trees. Seeds that are carried away, stored for later, and then forgotten can germinate away from their parent tree, the release states.

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Early Jurassic Basal Mammals Were Specialized Eaters

August 25, 2014

John Hopton for redOrbit.com – Your Universe Online

Researchers from several British universities have found that small Jurassic mammals chose very specific diets from among the smorgasbord of insects available to them, with creatures of a similar type having distinct food choices.

Using a combination of technologies and comparisons with living animals, the researchers were able to study patterns of wear and tear on the mammals’ teeth in fossils. The observations showed that some “shrew-sized” mammals from the early Jurassic period ate harder insects such as beetles, while others consumed softer ones like scorpion flies.

The study of the creatures, which had lived in the South Wales area of the UK around 200 million years ago and had previously been thought to be “generalized insectivores,” assists in our broader understanding of evolutionary processes at a time when new characteristics were developing in mammals, such as better hearing and teeth capable of precise chewing.

The researchers from the universities of Bristol, Leicester and Southampton studied jaw mechanics and fossil teeth in two mammals, Morganucodon and Kuehneotherium, and reported in the journal Nature that they had developed specialized diets. They said that the mammals had different techniques for catching prey as well as for chewing it.

Specialist procedures were required in order to conduct the study, and according to Dr. Pamela Gill from Bristol, “None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth. Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology.”

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Small mammals rapidly become extinct in small forest fragments

Near-complete extinction of native small mammal fauna 25 years after forest fragmentation

September 2013. As tropical forests continue to be felled and fragmented around the world. A key question is how rapidly species disappear from forest fragments and how quickly humans must restore forest connectivity to minimize extinctions.

Luke Gibson, a biologist at the National University of Singapore, & colleagues surveyed small mammals on forest islands in Chiew Larn Reservoir in Thailand from 5-7 and 25-26 years after isolation and observed the near-total loss of native small mammals within 5 years from islands smaller than 10-hectares and within 25 years from 10-56 hectare islands.

Based on these results, they developed an island biogeographic model and estimated mean extinction half-life (50% of resident species disappearing) to be 13.9 years. These catastrophic extinctions were probably partly driven by an invasive rat species; such biotic invasions are becoming increasingly common in human-modified landscapes. These results are thus particularly relevant to other fragmented forest landscapes and suggest that small fragments are potentially even more vulnerable to biodiversity loss than previously thought.

We surveyed small mammals on forest islands in a reservoir five separate times after isolation to assess the rate of species loss from forest fragments. Reservoirs can form useful natural laboratories to estimate extinction rates from isolated forest patches . 

Chiew Larn Reservoir

Chiew Larn Reservoir in southern Thailand was formed in 1986-1987 when 165 km2 of forest was flooded, creating over 100 islands in the process (Fig. 1) (17). We selected 16 islands in the reservoir ranging from 0.3 to 56.3 ha in area and surveyed small mammal communities 5 to 7 years (for 12 of the 16 islands) and 25 to 26 years after isolation.

Continued