Reintroduced Eurasian otters in Italy 621


TABLE 4 Year of sampling, amplified loci and amplification success for the six otters genotyped. Locus


2016


OT-14 OT-04 Lut 453 OT-17 Lut 833 Lut 701 Lut 818 OT-19 Lut 435 Lut 715 Lut 902


Amplification success (%)


Otter 1 129–129


177–190 127–131 151–172 163–175 207–247 160–170 215–215 129–143 203–203 145–166 100.0


2017


Otter 2 129–129


177–177 123–131 147–151 154–175 207–247


123–143 203–203


72.7


Otter 3 129–129


127–131


140–140 215–215 129–143 203–203


54.5


Otter 4 129–129


177–177 127–127 151–151 163–175


211–215 143–143 203–203 145–145 81.8


Otter 5 129–129


177–177 127–127 151–151 163–175 247–247 156–170 211–215 143–143 203–203 145–166 100.0


2018


Otter 6 129–129


166–177 127–127 151–151 165–165


170–170 215–215 143–143 203–203


81.8


(alleles that are lethal when homozygous or a collection of genes considered to be equivalent) per diploid individ- ual (0.0–12.58, increments of 0.629), carrying capacity (K = 15–60, increments of 5), per cent frequency of catastrophic events (1–10%, increments of 1%) and severity of the latter for reproduction (0.1–1.0, increments of 0.1).


Results


Of the 25 faecal samples stored for genetic analyses (21 from monitoring in 2016–2017 and four from 2018), eight (32%) were successfully genotyped, allowing us to identify six individuals (five and one, respectively; Table 4), along a c. 36 km long stretch of the river (Fig. 1). The distance between faecal samples from the same individual was 4–11 km. Twolociweremonomorphic and nine polymorph- ic (mean = 2.9 alleles per locus; maximum = 5 alleles for OT-04), for a total of 32 alleles. Expected heterozygosity (He) was 0.35 ± SE 0.07, and observed heterozygosity (Ho) was 0.41 ± SE 0.08. We obtained a region of mtDNA 175 base pairs long for


three of the seven analysed samples. All individuals shared an identical haplotype (Fig. 2) that was the same retrieved in the otter found as roadkill. All the Asian haplotypes were characterized by a transversion (A instead of G) at position 16.400 of the European lineage (Genebank accession no. MN122838). The same mutation was also found in the haplotype from the River Ticino. Population size in 2016–2017 was consistent with popu-


lation viability analysis models with N0 = 2 and the supple- mentation of four individuals in the following 2 years (two per year; scenario 1), despite a high probability of extinction in the first decade post-release (Fig. 3). The reintroduction of such a small number of individuals would be insuffi- cient to ensure the long-term survival of the population (P100,0.1; Fig. 3). For all scenarios, an initial phase of population growth,


FIG. 1 Distribution of genotyped otter Lutra lutra spraints (2016–2018) on the River Ticino, Italy.


with a peak of 4–33 individuals (,K) 15–20 years after the reintroduction, was followed by a progressive decline lead- ing toN100,N0 for all models, except for those of scenario 1 based on the concurrent release of 2–3 pairs (N100 = 12 and 20 individuals, respectively). As expected, for most models the probability of extinction in the first decade post-release was high (c. 70%).


Oryx, 2022, 56(4), 617–626 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321000107


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