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Inactivity/sleep in two wild free-roaming African elephant matriarchs – Does large body size make elephants the shortest mammalian sleepers?

View Article: PubMed Central - PubMed

ABSTRACT

The current study provides details of sleep (or inactivity) in two wild, free-roaming African elephant matriarchs studied in their natural habitat with remote monitoring using an actiwatch subcutaneously implanted in the trunk, a standard elephant collar equipped with a GPS system and gyroscope, and a portable weather station. We found that these two elephants were polyphasic sleepers, had an average daily total sleep time of 2 h, mostly between 02:00 and 06:00, and displayed the shortest daily sleep time of any mammal recorded to date. Moreover, these two elephants exhibited both standing and recumbent sleep, but only exhibited recumbent sleep every third or fourth day, potentially limiting their ability to enter REM sleep on a daily basis. In addition, we observed on five occasions that the elephants went without sleep for up to 46 h and traversed around 30 km in 10 h, possibly due to disturbances such as potential predation or poaching events, or a bull elephant in musth. They exhibited no form of sleep rebound following a night without sleep. Environmental conditions, especially ambient air temperature and relative humidity, analysed as wet-bulb globe temperature, reliably predict sleep onset and offset times. The elephants selected novel sleep sites each night and the amount of activity between sleep periods did not affect the amount of sleep. A number of similarities and differences to studies of elephant sleep in captivity are noted, and specific factors shaping sleep architecture in elephants, on various temporal scales, are discussed.

No MeSH data available.


Distance between sleeping herds.                        Bar graph showing the distance (kilometres, km) between                            sites of the major sleep episode of Matriarch 1 and Matriarch 2 on each                            day of the recording period when sleep occurred. The average distance                            between the sites of the major sleep episode for the two elephants on                            the same day was 9.3 km (s.d. = 8.1 km, range = 0.15–34.05 km).                            The closest the two matriarchs (and their respective herds) came to                            sleeping in the same location was 150 m, but on other days they could be                            over 34 km apart.
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pone.0171903.g007: Distance between sleeping herds. Bar graph showing the distance (kilometres, km) between sites of the major sleep episode of Matriarch 1 and Matriarch 2 on each day of the recording period when sleep occurred. The average distance between the sites of the major sleep episode for the two elephants on the same day was 9.3 km (s.d. = 8.1 km, range = 0.15–34.05 km). The closest the two matriarchs (and their respective herds) came to sleeping in the same location was 150 m, but on other days they could be over 34 km apart.

Mentions: The two elephants monitored slept in new locations on every day of the recording period (Table 3). The straight-line distance between the locations of the main sleep episodes for Matriarch 1 averaged 7.2 km (s.d. = 8.2 km; range = 0.8–40.2 km) and for Matriarch 2 averaged 6.9 km (s.d = 7.4 km; range = 0.5–29.1 km) (Fig 6). The actual distance travelled between each sleep location between main sleep episodes averaged 16.1 km (s.d. = 13.2 km; range = 5.1–66.4 km) for Matriarch 1 and 17.3 km (s.d. = 9.9 km; range = 7.7–51.5 km range) for Matriarch 2 (Fig 6). While inhabiting the same general area of the Chobe National Park, the two elephants did not sleep in the same location on any of the days recorded, meaning that the herds led by these two matriarchs did not appear to merge during the recording period, at least for sleeping. The average distance between the sites of the major sleep episode for the two animals on the same day was 8.9 km (s.d. = 7.9 km, range = 0.15–34.05 km) (Fig 7). Thus, the closest the two matriarchs (and their respective herds) came to sleeping in the same location was 150 m, but on other days they could be over 34 km apart.


Inactivity/sleep in two wild free-roaming African elephant matriarchs – Does large body size make elephants the shortest mammalian sleepers?
Distance between sleeping herds.                        Bar graph showing the distance (kilometres, km) between                            sites of the major sleep episode of Matriarch 1 and Matriarch 2 on each                            day of the recording period when sleep occurred. The average distance                            between the sites of the major sleep episode for the two elephants on                            the same day was 9.3 km (s.d. = 8.1 km, range = 0.15–34.05 km).                            The closest the two matriarchs (and their respective herds) came to                            sleeping in the same location was 150 m, but on other days they could be                            over 34 km apart.
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Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC5382951&req=5

pone.0171903.g007: Distance between sleeping herds. Bar graph showing the distance (kilometres, km) between sites of the major sleep episode of Matriarch 1 and Matriarch 2 on each day of the recording period when sleep occurred. The average distance between the sites of the major sleep episode for the two elephants on the same day was 9.3 km (s.d. = 8.1 km, range = 0.15–34.05 km). The closest the two matriarchs (and their respective herds) came to sleeping in the same location was 150 m, but on other days they could be over 34 km apart.
Mentions: The two elephants monitored slept in new locations on every day of the recording period (Table 3). The straight-line distance between the locations of the main sleep episodes for Matriarch 1 averaged 7.2 km (s.d. = 8.2 km; range = 0.8–40.2 km) and for Matriarch 2 averaged 6.9 km (s.d = 7.4 km; range = 0.5–29.1 km) (Fig 6). The actual distance travelled between each sleep location between main sleep episodes averaged 16.1 km (s.d. = 13.2 km; range = 5.1–66.4 km) for Matriarch 1 and 17.3 km (s.d. = 9.9 km; range = 7.7–51.5 km range) for Matriarch 2 (Fig 6). While inhabiting the same general area of the Chobe National Park, the two elephants did not sleep in the same location on any of the days recorded, meaning that the herds led by these two matriarchs did not appear to merge during the recording period, at least for sleeping. The average distance between the sites of the major sleep episode for the two animals on the same day was 8.9 km (s.d. = 7.9 km, range = 0.15–34.05 km) (Fig 7). Thus, the closest the two matriarchs (and their respective herds) came to sleeping in the same location was 150 m, but on other days they could be over 34 km apart.

View Article: PubMed Central - PubMed

ABSTRACT

The current study provides details of sleep (or inactivity) in two wild, free-roaming African elephant matriarchs studied in their natural habitat with remote monitoring using an actiwatch subcutaneously implanted in the trunk, a standard elephant collar equipped with a GPS system and gyroscope, and a portable weather station. We found that these two elephants were polyphasic sleepers, had an average daily total sleep time of 2 h, mostly between 02:00 and 06:00, and displayed the shortest daily sleep time of any mammal recorded to date. Moreover, these two elephants exhibited both standing and recumbent sleep, but only exhibited recumbent sleep every third or fourth day, potentially limiting their ability to enter REM sleep on a daily basis. In addition, we observed on five occasions that the elephants went without sleep for up to 46 h and traversed around 30 km in 10 h, possibly due to disturbances such as potential predation or poaching events, or a bull elephant in musth. They exhibited no form of sleep rebound following a night without sleep. Environmental conditions, especially ambient air temperature and relative humidity, analysed as wet-bulb globe temperature, reliably predict sleep onset and offset times. The elephants selected novel sleep sites each night and the amount of activity between sleep periods did not affect the amount of sleep. A number of similarities and differences to studies of elephant sleep in captivity are noted, and specific factors shaping sleep architecture in elephants, on various temporal scales, are discussed.

No MeSH data available.