Fast living vs. slow and steady

Fast living makes headlines, as evidenced by such notables as Freddie Mercury, Paul Walker and Lamar Odom.  Unfortunately the first two are dead while Odom was narrowly brought back from a near-death experience – all were victims of their fast life styles.  Like humans, some birds live fast and die young, while others live slow, but may survive to relatively ripe old ages.

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The tiny rifleman (Acanthisitta chloris), reintroduced in Tiritiri Matangi, New-Zealand.  This endangered bird feeds on insects that it gleans from tree trunks.  It often has two clutches of 2-5 young per year. Credit: Simon Ducatez.

Simon Ducatez studied invasive cane toads with Rick Shine in Australia, and became interested in why some species were more likely than others to successfully invade new habitat.  The problem for answering that question is that most invasions are not studied until after the invasive species becomes established; by that time it may be too late to identify exactly what factors were responsible for the successful invasion. On his first visit to New-Zealand in 2016, Ducatez discovered ecosanctuaries – enclosed wildlife reserves where invasive predators are eliminated, and native animals (mostly birds) are introduced. He realised that these introductions could provide invaluable information on why species thrive or fail to become established in a new environment. At about the same time, a colleague drew his attention to a database developed by the Lincoln Park Zoo (LPZ) in Chicago, Illinois, which contains data on hundreds of intentional release events (translocation attempts), including information on the survival and reproduction of the released individuals. Analyzing how a species life history could affect the survival and reproduction of these voluntarily introduced populations would provide answers useful for restoration biologists who wish to return native species to habits where they were now extinct, and to ecologists who want to identify the factors promoting biological invasions.

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The relatively massive and flightless south island takahe (Porphyrio hochstetteri), reintroduced in New-Zealand.  This bird was thought to be extinct but was rediscovered in 1948 and has benefited from active restoration programs. Credit: Simon Ducatez.

Life history traits are adaptations that influence growth, survivorship and reproduction of individuals of a particular species.  For each species in the LPZ dataset, Ducatez and Shine used the bird literature to gather data on body mass and four life history traits: maximum lifespan, clutch size, number of clutches per year, and age at first reproduction. They then used a statistical procedure – principle components analysis – which described each species based on their life history strategy.  Fast life styles were associated with small bodies, short lifespans, large clutch size and number, and early reproduction.  Slow life styles were associated with large bodies, long lifespans, small clutch size and number, and delayed reproduction. Ducatez and Shine then asked a simple question based on 1249 translocation events in the LPZ dataset – how do fast life style birds perform in comparison to slow life style birds following translocation?

It turns out that slow life style birds are much better at surviving translocation than are fast life style birds, at least when measured in the short term (one week) and the medium term (one month).

DucatezFig1ab

Association between life style as measured by principle component analysis (PC1 on X-axis) and survival (proportion of translocated individuals still alive on Y-axis). The left graph is survival to one week, while the right graph is survival to one month. 

In contrast, following translocation fast life style birds are more likely to attempt breeding and successfully breed than are slow life style birds.

DucatezFig1cd

Association between life style and probability of attempting breeding (left graph) and successfully breeding (right graph).

Ducatez and Shine suggest that both restoration biologists and invasion ecologists could use these findings to address major questions in their respective fields.  Restoration biologists wishing to return native species to previously occupied habitat might adopt different approaches based on a species life style. Species with fast life styles suffer from low survival, so restoration biologists should focus on promoting survival by controlling predators or provisioning extra food. Species with slow life styles suffer from low reproductive success, so conservation managers might consider providing extra nest boxes or other resources that promote successful breeding.

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A successful foraging event for an Atlantic puffin (Fratercula arctica), reintroduced in Maine, USA. Credit: Simon Ducatez.

This research informs invasion ecologists that the same trait can have opposite effects on the likelihood that a biological invasion will actually happen.  Thus a slow life style species is more likely to survive moving to a novel habitat, but is unlikely to breed successfully once it gets there.  In contrast a fast life style species is less likely to survive the move, but if it does survive, it may be more likely to successfully reproduce. How this plays out in actual biological invasions is yet to be determined, but at least we now have a better grasp on what factors we should be examining.

note: the paper that describes this research is from the journal Conservation Biology. The reference is Ducatez, S. and Shine, R. (2019), Life‐history traits and the fate of translocated populations. Conservation Biology, 33: 853-860. doi:10.1111/cobi.13281. Thanks to the Society for Conservation Biology for allowing me to use figures from the paper. Copyright © 2019 by the Society for Conservation Biology. All rights reserved.

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