Science - USA (2020-07-10)

with increasing time since tagging (linear re-
gression,r^2 = 0.001,P= 0.48; Fig. 3D) or differ
among age groups (ttest,t=−0.38,P= 0.72) or
forearm lengths (linear regression,r^2 = 0.01,
P= 0.47). Following an informed untagged
conspecific as an alternative explanation for
shortcutting is highly unlikely, given the
very rare incidence in our dataset of two

tagged individuals flying within reasonable

distance (250 m) and time (10 s) of each other

(37 track pairs were only partly overlapping

within these parameters, totaling 0.4% of flight

localizations). Overall, shortcuts or unrecorded

routes were fairly common, very straight, and

indistinguishable from the bats’regular re-

peated tracks between any two known loca-

tions for both juveniles and adult bats. These

results matched our predictions and suggest

superior map-like spatial knowledge with

no decay in spatial memory for at least up to

158 nights, likely acquired within the first 3

months of life.

To reduce uncertainty about bats’previ-

ous experience within their home range, we

SCIENCEsciencemag.org 10 JULY 2020•VOL 369 ISSUE 6500 191

shortcuts

(8821)

Shortcuts

(397)

Trans.

returns

(22)

After trans.

returns

(409)

1

0.9

0.8

0.7

0.6

0.5

0.4

Straightness index

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

0 40 80 12 0 16 0

Shortcut straightness index

Nights since tagging

Turning anglesGoal headings

A B

C D

Fig. 3. Shortcuts and translocation experiments.(A)All tracks classified as
shortcuts or unrecorded routes (n= 397) taken by 70 bats. (B) Movement
tracks of translocated bats. Red stars mark the three release sites located 10,
14 and 16 km from the site of capture, in black are the return tracks and in
orange are all the tracks subsequently made by these bats. Only one of the
22 translocated bats returned to the vicinity of the release site. (C) (Top)

boxplots of straightness index for nonshortcut tracks, all shortcuts, return tracks

of translocated bats, and tracks of translocated bats after returning (number

of tracks in parentheses). (Bottom) turning angles (blue) and headings relative

to goal (orange) of all nonstationary localizations within these categories.

(D) Shortcut straightness index as a function of nights passed since tagging

before the shortcut was made.

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