Four-wing saltbush (Atriplex canescens) seed and seedling consumption by granivorous rodents

Authors: Clements, Darin - Charlie; Harmon, Daniel - Dan

Submitted to: Rangelands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2017
Publication Date: 12/7/2017
Citation: Clements, D.D., Harmon, D.N. 2017. Four-wing saltbush (Atriplex canescens) seed and seedling consumption by granivorous rodents. Rangelands. 39(6):182-186. https://doi.org/10.1016/j.rala.2017.10.002.
DOI: https://doi.org/10.1016/j.rala.2017.10.002

Interpretive Summary: Four-wing saltbush is an important browse species to wildlife and livestock and has been reported to provide as much as 11.4% to 13.6% crude protein3. The use of four-wing saltbush in restoration and land rehabilitation plantings is well documented and increasingly popular. Granivorous rodents are important in the ecology of plant communities as well as the management practices that occur in those communities. Four-wing saltbush has been reported to experience quite variable success in seeding efforts as poor seed germination or lack of proper amount and periodicity of precipitation would fit under the abiotic category and are more acknowledged. Biotic factors such as seed and seedling predation by granivorous rodents are less understood. This study was initiated to address: 1) The harvest, consumption, and caching of four-wing saltbush seed, and 2) the possible consumption of four-wing saltbush seedlings by granivorous rodents. We hypothesized that granivorous rodents in this study would harvest, consume and cache a portion of the four-wing salt-bush seed they interacted with. We also hypothesized that four-wing saltbush seedlings would also be consumed by granivorous rodents in this study. Granivorous rodents in this study consumed as much as 55 and 99% of the four-wing saltbush seed and seedlings, respectfully. Although this research was conducted using portable enclosures, granivorous rodents in this study avoided caching four-wing saltbush seed while still excavating the embryo from the seed. The seedling predation may well be higher than in natural conditions, yet the fact that such a high level of seedling predation occurred when an alternative millet seed food source was available suggest a preference for these seedlings at this young phenology stage. This research yielded that four-wing saltbush seed is not highly preferred as the rodents at this site are not harvesting and caching the seed for future consumption. The high consumption of four-wing saltbush seedlings at this site is alarming however, and may be an explanation of poor success at given sites following the seeding of four-wing saltbush.

Technical Abstract: Four-wing saltbush (Atriplex canescens [Pursh] Nutt.), native to western North America, extends from Canada to Mexico and from the Great Plains to the Pacific Coast. Shrubby species of Atriplex are in the family Chenopodiacea, which contains other important shrubs such as winter fat (Krascheninnikovia lanata Pursh), and often dominate landscapes in many arid and semi-arid regions, particularly in habitats that combine high soil salinity with aridity1. Four-wing saltbush is an important browse species to wildlife and livestock and has been reported to provide as much as 11.4 % to 13.6% crude protein. Granivorous rodents are important in the ecology of plant communities as well as the management practices that occur in those communities. Granivorous rodents exhibit two types of seed caching behavior; they cache some seeds in larders deep within their burrows, referred to as “larder hoarding”, and cache some seeds in shallow depressions they dig throughout their home range, referred to as “scatter hoarding”. Larder hoard caches are buried at depths that may allow germination but are most often too deep to sprout, whereas scatter hoard caches that are not recovered are buried at depths that often promote germination and therefore have been found to be an important mechanism for the recruitment of various range plants. This study was initiated to address: 1) The harvest, consumption, and caching of four-wing saltbush seed, and 2) the possible consumption of four-wing saltbush seedlings by granivorous rodents. Investigation of rodents (n = 103) with four-wing saltbush seed in the portable enclosures revealed that none of the 103 rodents harvested four-wing saltbush seed in their cheek pouches or cached any seed in the portable enclosure. Therefore, there was no evidence that rodents were attempting to cache four-wing saltbush seed. The Merriam’s and Desert kangaroo rat as well as the White-tailed antelope ground squirrel significantly (P = 0.0001) consumed four-wing saltbush seed. The Desert kangaroo rat consumed the most four-wing saltbush seed, 55.11 (± 3.22), n = 29, followed by the Merriam’s kangaroo rat, 54.70 (± 2.20), n = 62, White-tailed antelope ground squirrel, 34.33 (± 8.14), n = 5, and the chisel-toothed kangaroo rat, 13.63 (± 6.60), n = 7. The consumption of four-wing saltbush seedlings by these rodents was very high as the Desert kangaroo rat consumed an average of 99.25 (± 6.62), n = 12, Merriam’s kangaroo rat, 92.94 (± 3.00), n = 51, and the chisel-toothed kangaroo rat, 74.59(± 5.01), n = 23, even though millet seed was available as an alternative food source and that the 4 g of millet seed available was never totally consumed. Although this research was conducted using portable enclosures, granivorous rodents in this study avoided caching four-wing saltbush seed while still excavating the embryo from the seed. The seedling predation may well be higher than in natural conditions, yet the fact that such a high level of seedling predation occurred when an alternative millet seed food source was available suggest a preference for these seedlings at this young phenology stage.