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Economy of autotomy (shedding less than complete tails) is advantageous via retention of ability to autotomize and reduction of costs, including lipid loss, regeneration, and decreased social status. We studied its effects on predator-distracting tail movements and running speed in the speckle-lipped mabuya (Trachylepis maculilabris (Boettger, 1913)) by removing fractions of the autotomizable portion. Distance moved was shorter for autotomized tail segments one third of the total tail length than for longer segments. Movement duration did not vary with proportion removed. Longer movement suggests that shedding longer segments improves ability to distract predators, enhances difficulty of capturing a tail, and may require longer handling time. Tails were difficult to break in regenerated sections and did not move when broken. The lack of movement of regenerated portions after separation suggests permanent loss of capacity to distract predators. Decreased speed was confirmed as a cost of autotomy in lizards that lost at least two thirds of their tail. In lizards that lost one third of tails speed was intermediate to that of intact lizards and those that lost more. Graded decrease in speed as proportional loss increases is consistent with progressive loss of a counterweight that reduces lateral motion while running. Economy of autotomy entails trade-offs between immediate and long-term escape ability. Une economie lors de l'auotomie (la perte de moins que la totalite de la queue) est avantageuse a cause du maintien de la capacite d'autotomie subsequente et de la reduction des couts, en particulier ceux lies a la perte de lipides, la regeneration et la reduction de statut social. Nous avons etudie les effets de cette economie sur les mouvements de la queue destines a detourner l'attention du predateur et sur la vitesse de course chez le scinque aux levres tachetees (Trachylepis maculilabris (Boettger, 1913)) en amputant des fractions de la portion autotomisable. La distance de deplacement est plus courte pour les segments d'un tiers de la longueur totale de la queue que pour les segments plus longs. La duree des mouvements ne varie pas en fonction de la portion enlevee. Les mouvements plus grands indiquent que la perte de segments plus longs augmente la capacite de detourner l'attention des predateurs, accroit la difficulte de capturer la queue et pent augmenter le temps de manipulation. Les queues sont difficiles a briser dans les sections regenerees et elles ne bougent pas une fois brisees. La perte de mouvement des portions regenerees apres la separation laisse croire a une perte permanente de la capacite de detourner l'attention des predateurs. Nous confirmons qu'une reduction de la vitesse est un cout de l'autotomie chez les lizards qui perdent an moins deux tiers de leur queue. Chez les lizards qui ont perdu un tiers de la queue, la vitesse est intermediaire entre celle de lizards intacts et de lizards qui en ont perdu plus. Une diminution graduelle de la vitesse en proportion directe de la perte de queue est conforme a la perte progressive d'un contrepoids qui reduit les mouvements lateraux durant la course. Une economie dans l'autotomie implique des compromis entre les capacites immediate et a long terme de fuite. [Traduit par la Redaction], Introduction Autotomy is an antipredatory defense that allows prey to escape via loss of expendable body parts that may distract predators, but its use is costly (Wilson and Booth 1998; [...]

Data on natal dispersal distances (NDDs) of golden eagle Aquila chrysaetos in North America are needed to define local area populations and inform decisions authorizing take (i.e., injury, death, or disturbance) of the species via federal permit. Sixteen golden eagles (6 males, 10 females) tagged with satellite transmitters as ∼8-wk-old nestlings in the southwestern United States during 2010–2013 dispersed a mean of 55.3 km (SD = 29.7, median = 64.5), either 1) between their natal nest sites and nests where they first bred (n = 3 females, all subadults, i.e., in their fourth year of life), or 2) between natal sites and where they permanently settled as adults at least in their fifth year of life, but did not necessarily breed (i.e., exhibiting only gross natal dispersal). On average, females dispersed about 50% farther than males; mean NDD of males and females was 41.2 km (90% credible interval = 11.1–75.2) and 63.8 km (44.8–82.6), respectively. Median NDD of males and females was 41.5 and 65.8 km, respectively; in a Bayesian framework, the estimated difference in posterior median distributions of male and female NDDs was 22.2 km (−15.7 to 57.3; P ≠ 0 = 0.89), tentatively indicating that NDD of golden eagles in our study area may be female biased. Although our findings are based on a relatively small data set including both effective and gross natal dispersal records, they represent the first comparison of NDD between sexes of golden eagle in North America and the first published records on the continent of the species' NDD based on telemetry methods. More work is needed to validate whether golden eagle NDD in at least some regions of North America is female biased, which could have important implications for authorizing take of the species. [ABSTRACT FROM AUTHOR]