Dear MARMAM subscribers, on behalf of my colleagues I am pleased to share with you our recent publication: Piero Manfredi, Luigi Marangi, Alessia Rossi, Giovanni Santangelo (2016). An improved model life table for the Indian River Lagoon bottlenose dolphin population and remarks on early mortality. Marine Mammal Science. 32(4): 1522-1528. http://onlinelibrary.wiley.com/doi/10.1111/mms.12334/abstract Abstract: Substantial dolphin population mortality occurs during the first few years of life (Mann and Watson-Capps 2005), with evidence of up to 50% of newborns eliminated by age 4 (Stolen and Barlow 2003, Mannocci et al. 2012). In particular, the first year of life is the most cryptic period for marine mammals, making it important to understand the underlying mortality process in depth. An important source of information for age-specific bottlenose dolphin mortality is the stranding data set of the Florida Indian River Lagoon population (IRL), for which age at death at completed years was reconstructed by counting dentinal growth layer groups (Stolen and Barlow 2003). A theoretical life table was built on such data by Stolen and Barlow (2003), by fitting Siler’s parametric model (Siler 1979) to the age at death of 220 stranded individuals, yielding useful information on the mortality pattern of this population. In the Siler model the age-specific hazard of mortality is given by the sum of three components: an exponentially declining one; a constant one; and an exponentially increasing component, which is senescence-related. The Siler model provides an excellent fit for many real populations, supported by clear biological interpretations of its parameters. A possible shortcoming of Stolen and Barlow’s approach is that the Siler model was proposed for the IRL data on a priori grounds, i.e., as a flexible model for a wide range of long-lived species, without preliminary discussion on its full appropriateness for the data considered. Indeed, retaining Stolen and Barlow’s (2003) baseline assumption of a stationary population (i.e., a stable age distribution with an intrinsic growth rate equal to zero; see Caswell 2001), inspection of the resulting observed age-specific hazard of mortality in the first few years of life does not robustly support the initial exponential decline postulated by the Siler model: the mortality rate is high (about 18%/yr) at age 0, it declines to about 10% at age 1, it climbs back to more than 20% at age 2, and then stays constant in the region of 12% in the two subsequent age groups, before declining quite rapidly to a bottom rate (around 3.5%/yr on average) which remains roughly constant between age 6 and 15. Similar patterns have been observed also in other published data (Mannocci et al. 2012). The above-described pattern in the data indicates as more plausible the alternative hypothesis of a roughly constant hazard of mortality in the first 5 yr of life, followed by a rather rapid decline before bottoming out, prior to the final onset of the exponentially increasing phase. We therefore propose, as an alternative to the Siler model, a new model, termed ReLogit for ease, replacing the exponentially declining component for early mortality with three-parameter “reversed-logistic” curve. Please contact me by email (arossi@biologia.unipi.it) for the full text. I will be glad to send you a pdf copy. Kind regards Alessia Rossi -- PhD Alessia Rossi Biology Department (Zoology - Animal Ecology) - Demography and Conservation Laboratory via A.Volta, 6 - 56126 Pisa, Italy Cell: +393494743502. e-mail: arossi@biologia.unipi.it skype: musicale85