Causes of the Decrease in the Number of Ermine (Mustela Erminea L., 1758) and Pelt Procurement in Yakutia

Abstract

During the last four decades, a decrease in ermine pelt procurement has been noted in Yakutia. To determine the possible reasons for this, material on the ecology of ermine and sables in Northeast Yakutia was collected from 1980–1994. The study examined 2890 sable stomachs for feed, and 1167 ermine skulls for Skrjabingylus infection. It was revealed that ermine are hunted by sables, but their proportion of the diet is low (0.4–3.4%). It was found that sables displaced ermine from the taiga biocenosis. The most acute effects of this process occurred during the sable settlement in October–November and are exacerbated by small numbers of rodents and crop failure in the main taiga feed. The overall intensity of infestation with the Skrjabingylus nasicola nematode was 19%, suggesting that this parasite is unlikely to have significantly affected the number of ermine.

Keywords

Ermine ; Mustela erminea ; Number ; Fur harvesting ; Sable ; Skrjabingylus ; Yakutia

Introduction

Ermine are widely distributed in the taiga and tundra of Yakutia up to the coast of the Arctic Ocean, but their distribution is uneven. The habitats are very diverse, but generally, the ermine are found in river valleys (Tavrovsky et al., 1971 ).

In the 1940s, Yakutia was the main supplier of ermine pelts in the Soviet Union (up to 80%). Ermine pelts made up 11.5% of the total export of furs during that period. However, over the past 20 years, the procurement of ermine pelts has decreased to a very low level. A similar trend has been observed in the Krasnoyarsk region since 1954 (Syroechkovsky, 1974 ) and in Sayan (Sokolov, 1979 ). It was assumed that this trend was caused by the growing number of sables (Martes zibellina ) and their migration. As a result, sable ousted ermine from the taiga regions ( Syroechkovsky, 1974 ). However, it was previously noted that the population dynamics of the ermine can also be influenced by the incidence of Skrjabingylus infection ( Lavrov, 1944  and Kontrimavichus, 1969 ).

To determine the causes of the sharp decline in ermine pelt procurement in Yakutia, a study was performed to analyse the ecology of the ermine, sable nutrition and data on the number of ermine, sables and small rodents.

Materials and Research Methodology

From 1980 to 2011, material was collected on the ermine ecology of Western, Central and Northeast Yakutia. Most of the field data were collected in three areas of Northeast Yakutia: from 1980–1994, samples were collected at the Yakutia Branch of the All-Union Scientific Research Institute of Hunting and Farming (YB AUSRIHF) station, located in the foothills of Verkhoyansk (in the Belyanka river basin, Kobyaisky district, Lena right bank); from 1986–1989, the samples were collected at the stations located in the territory of Srednekolymsky and it the Verkhnekolymsky districts.

During this period, the samples covered an area of 1545 km, with 1184 ermine carcasses and 2890 sable stomachs being processed. The census of ermine, sables and small rodents was conducted at the same stations. The census of mammals was implemented in accordance with the methodology described by Novikov (1953) .

The present article contains material from YB AUSRIHF (ermine and sable necropsy logs for the period from 1951 to 1993, accounting data) and other departmental organisations (The Department of Biological Resources of the Ministry of Environmental Protection of Yakutia, SUE FAIC “Sahabult”, the Federal State Statistics Service of Yakutia).

Former employees of the Yakut Branch AUSRIHF include M.Z. Gotovtseva, R.K. Anikin, V.V. Plesnivtsev, M.I. Larionov and V.V. Sokolov, with whom V.T. Sedalischev worked from 1980 to 1994. All of these individuals took part in the collection and processing of materials.

Dynamics of the Ermine Pelt Procurement

During the period from 1950–1960, the average number of ermine pelts procured in the entire country was 125,000, with a maximum of 225,000 (in 1953) and a minimum of 95,000 (in 1955).

Since the mid-1970s to the late 1980s, ermine comprised approximately 5.4% of the total furs produced in the country. This makes it the fifth most common fur harvested after sable, muskrat (Ondatra zibetica ), squirrel (Sciurus vulgaris ) and arctic fox (Alopex lagopus ). During these years, the average procurement of the species was 48,600 pelts, with a maximum of 70,400 (in 1975) and a minimum of 38,100 (in 1982). The greatest number of pelts procured during this period originated from the north-eastern regions, where the average annual procurements amounted to approximately 15,000 pelts. In the central and western regions, 6300 and 5500 pelts were procured, respectively ( Sedalischev and Odnokurtsev, 2006 ).

The downward trend in ermine fur procurement in the republic that began in the 1970s has been continuing to the present time. Thus, for the periods from 1980–1989 and 1990–1999, the average annual number of ermine pelt procurement in the region was 47,000 and 24,700, respectively. In the period from 2000–2009, there was a further decrease, with an estimated average of 9000 ermine pelts procured per year (Table 1 ).

Table 1. The dynamics of ermine pelt procurement in the area of Yakutia during the period from 1930–2011.

Area	Yearly average pelts procured, thousand units
	1930–1939	1940–1949	1950–1959	1960–1969	1970–1979	1980–1989	1990–1999	2000–2009	2010	2011
Western (Vilyuisk)	36.0	21.2	25.4	15.3	8.0	6.8	4.0	2.4	0.8	0.8
Central	41.4	24.1	23.7	18.6	9.4	4.6	4.3	0.7	0.2	0.3
North-eastern	84.6	69.8	76.3	59.8	24.2	27.4	11.0	4.5	1.3	2.3
North-western	11.6	10.4	10.2	9.4	5.0	3.3	2.9	0.2	–	–
Aldanskaya (Southern)	8.4	3.0	4.1	2.4	2.3	0.6	0.8	0.4	–	–
South-western (Prilenskaya)	7.1	2.3	3.1	1.6	1.0	0.4	0.4	0.3	–	–
Tundra	8.3	7.1	9.0	6.6	3.1	3.9	1.3	0.5	–	–
Total	197.4	137.9	151.8	113.7	53.0	47.0	24.7	9.0	2.3	3.4

Results and Discussion

The relationships between sable and ermine in natural biological communities in places shared by these species are of interest to many parties, including ecologists and hunters. An analysis of the literature suggests that ermine sometimes are attacked by sables, but the influence of this factor on the ermine population is insignificant, at least in Yakutia (Table 2 ).

Table 2. Occurrence of ermine remains in the sable stomachs and excrements in different regions of Russia.

Region	Number of stomach and faeces samples	Period	Occurrence, %	Researchers
Yakutia
South Yakutia (Uldano-Uchursky Ridge)	122 (excrements)	Winter 1954	0.9	Melchinov (1962)
South Yakutia Olekma river	29 (excrements)	Winter 1975/76	3.4	Revin (1989)
South-western Yakutia	97 (stomachs)	Hunting season 1982/83	2.1	Sedalischev et al. (2011a)
North-western Yakutia (Olensky area)	264 samples 97 cases	Unknown Winter 1950/51	3.3 7.0	Tavrovsky (1958)
	25 (stomachs), 314 (excrements)	October–December 2003	0.4	Zakharov (2005)
Magadanskaya oblast	21 (excrements)	April 1983	14.3	Ivanov (1985)
North-western Siberia
Omolon river Omolon river Cholomdzha river	28 (stomachs) 200 (excrements) 12 (stomachs)	November–March 1979/80 January–May 1980 November–March 1980/81	3.5 0.5 5.3	Chernyavsky (1984)
Kamchatka	1336 samples	1957	0.5	Vershinin (1977)
Central Siberia
Evensky Autonomous District Putoran Plateau	26 (stomachs), 189 (excrements) 300 (stomachs and excrements)	Hunting seasons 1955–1960 Hunting seasons 1986–1993	0.3 1.7	Kiselev (1964)Begletsov (2002)
Western Siberia
Tomsk Oblast	83 (stomachs)	Winter 1952/53, January–February 1954, January–February 1955.	1.2	Kryzhanovskaya (1956)

However, in some cases, for example, in Northwest Yakutia, the incidence of finding ermine remains in the stomachs of sables was approximately 7%, but this was manifested only during the years when the number of rodents was limited, when both competing species starved (Tavrovsky, 1958 ). At the same time, a number of studies demonstrated that ermine remains were not found in the stomach contents or faeces of Yakut sables (Belyk, 1975 , Sedalischev, 2001 , Sedalischev et al., 2007 , Sedalischev et al., 2011b , Cheprosov and Mordosov, 2011  and Zakharov and Safronov, 2012 ). For example, between 1983 and 1996, the contents of the stomachs of 1884 sables caught in Srednekolymskiy District (Northeast Yakutia) were analysed, but ermine remains were not found in any of them (Sedalischev, 1998 ).

Buyakovich and Kornilov (1948) were the first to note that the hunting of ermine by sables was found only under certain conditions in Yakutia. The authors noted that sables hunted ermine more often during times of scarcity. Traces of such hunting were observed in the winter in 1950/51 in the Zhigansky area (Northwest Yakutia), when the number of rodents was low. Based on data obtained from a survey of hunters, these authors suggested that the consumption of ermine by sable may occur when the ermine are caught in traps.

According to the literature, the effect that sables have on the number of ermine is not so much in their physical extermination, but rather as ousting them from a specific region. That is evident in central Yakutia, where sables were found sporadically during the second half of the 1960s (Belyk et al., 1990 ), but where the species has recently settled in the areas on both the right and left banks of the Lena river (Sedalischev et al., 2007 ).

In mountainous areas, sable procurement began in 1970. Four sables were captured that year, and 521 ermine pelts were procured. The average number of traces on the 10 km route evaluated in the spring of 1970 in taiga habitats was equal to 1.12 ermine tracks, and 0.24 sable tracks.

An analysis of recorded data (Table 3 ) demonstrated that with the growth of the sable population, the ermine population declines. In 1990 and 2010, the number of traces on the same 10 km route decreased 1.6 and 3.2 times, respectively, compared with that in 1970, whereas the number of sables in 1990 and 2010 was increased by 6.1 and 6.0 times compared with that in 1970.

Table 3. Accounting indicators of the ermine and sable populations and their pelt procurement in the mountainous region (central Yakutia).

Year	Ermine			Sable
	Number of tracks per 10 km	Density units/1000 ha	Number of pelts procured	Number of tracks per 10 km	Density units/1000 ha	Number of pelts procured
1970	1.12	1.45	521	0.24	0.11	4
1971	3.22	4.18	1274	0.27	0.12	3
1972	4.13	5.37	2102	0.28	0.13	2
1973	2.21	2.87	1054	0.25	0.11	6
1974	1.20	1.56	677	0.29	0.13	19
1975	2.94	3.82	2078	0.37	0.16	46
1976	1.66	2.16	1074	0.39	0.17	50
1977	0.93	1.21	762	0.28	0.12	51
1978	0.78	1.01	484	0.26	0.11	44
1979	0.58	0.75	221	0.39	0.17	65
1980	1.14	1.48	254	0.45	0.20	95
1981	0.93	1.21	248	0.34	0.15	90
1982	1.44	1.87	949	0.38	0.17	112
1983	0.95	1.23	498	0.75	0.34	162
1984	0.87	1.13	541	0.52	0.23	247
1985	1.13	1.47	964	0.61	0.27	278
1986	0.89	1.56	503	0.92	0.41	545
1987	0.91	1.18	338	1.21	0.54	500
1988	1.12	1.45	597	2.65	1.19	623
1989	1.56	2.03	952	1.75	0.79	682
1990	0.69	0.89	544	1.46	0.66	645
1991	0.54	0.70	310	0.85	0.38	111
1992	0.42	0.55	186	0.61	0.27	225
1993	0.66	0.86	249	0.94	0.42	240
1994	0.45	0.58	84	1.23	0.55	283
1995	0.51	0.66	121	1.43	0.64	338
1996	0.54	0.70	197	0.92	0.41	151
1997	0.65	0.84	183	1.42	0.64	375
1998	0.44	0.57	99	1.49	0.67	231
1999	0.36	0.47	91	2.28	1.02	307
2000	0.57	0.74	142	2.15	0.97	347
2001	0.63	0.82	301	2.15	0.97	509
2002	0.37	0.48	86	1.21	0.54	285
2003	0.29	0.32	–	0.94	0.42	374
2004	0.34	0.37	38	2.98	1.34	484
2005	0.32	0.42	4	1.75	0.79	175
2006	0.26	0.34	–	0.85	0.38	422
2007	0.31	0.40	35	0.96	0.43	378
2008	0.34	0.44	–	1.12	0.50	450
2009	0.29	0.32	–	1.25	0.56	297
2010	0.35	0.38	–	1.43	0.64	216

Since 1990, the number of ermine has remained low. The ousting of ermine by sables may have occurred because of the competitive relationship between these species due to common food links (with a group of rodents).

Ermine is pronounced miofag in Russian (Belyk, 1962 , Ternovsky, 1969  and Tumanov and Smelov, 1980 ). The basis of the ermines diet is rodents. Sables are euryphagous, consuming diverse plants and animals (Belyk, 1975  and Bakeev et al., 2003 ).

The diet of sables in central Yakutia is very narrow and is different from that of animals living in other regions of Yakutia, such as the southwestern and southern regions (Belyk, 1975  and Revin, 1989 ) and compared with the western region (Sedalischev, 2001 ). Compared with the south Yakutian sables (Revin, 1989 ) central Yakutian animals (Sedalischev et al., 2007 ) do not eat northern pika (Ochotona hyperborea ), Korean field mice (Apodemus peninsulae ), or nuts of the Siberian pine (Pinus sibirica ) and Siberian dwarf pine (Pinus pumila ), and the occurrence of blueberries (Vaccinium uliginosum ) and lingonberries (Vaccinium vitis-idaea ) in the diet is insignificant. Moreover, the animal resources available as food for sables and ermine in central Yakutia are significantly reduced during the winter due to the strong reduction in the number of voles (Clethrionomys spp.) ( Safronov, 1983 ).

The displacement of ermine by sables from the taiga habitats was most noticeable in the years when there was a low number of rodents. For example, in September of 1983 and 1985, the numbers of rodents in the mountainous areas were very low (an average of 4.8 and 6.5 rodents were captured in a 100-space board per day, respectively). In October of those years, it was noted by the tracks that the sables were leaving their habitats to search for food, and the migrants often persecuted, and therefore superseded, the ermine, which were forced to leave the taiga habitats and colonise the large valleys and small rivers, canals, lakes shore, swamps and bushy (small willow) areas. A similar picture was observed in the “Belyanka” area (foothills of Verkhoyanye) from 1980 to 1993. Based on the long-term observations, the most common timing of this change in territory is in October, when yearlings begin to settle. In the foothills of Verkhoyanye, ermine mainly occupy the riparian habitats with willow and overgrown burnt areas, which are not common areas occupied by sables. For this reason, the ecological niches of the two predators do not match. However, the number of ermine was kept at a low level (0.74 to 0.89 individuals/1000 ha) for almost the entire study period, and the number of sables compared with the number of ermine was high (1.7 to 3.2 individuals/1000 ha).

In early October 1986, the snow cover reached 10–15 cm, and the number of voles was average (with an average of 19.4 rodents captured in a 100-space board per day), and there was a good crop of blueberries and dwarf Siberian pine nuts, so the nutritive base was favourable for sables. The relative population of ermine averaged 0.76 traces for a 10 km route (0.98 individuals/1000 ha) and 2.97 sable traces (1.34 individuals/1000 ha). Sable traces were observed with the first snow, but settling juveniles were noted at the end of the month, when the snow depth reached 20–25 cm. The sables moved along the rivers and streams until the first ten days of November, then the influx of animals stopped. During this season, three cases of sable attacks on ermine caught in traps were registered; however, none of the ermine was eaten. On October 8, 1996, during an inspection of ermine traps set on the river Hadarynya, sable traces following ermine traces were noted. The results of tracking showed that the sable had initially killed the trapped ermine, and then dragged it along with a trap for a distance of approximately 15 m, and left it afterwards.

In addition to the personal observations of numerous hunters, there was a survey (158 questionnaires) of hunters from Kirov farm, who were engaged in sable hunting in the Belyanka river basin. There were 15 reported cases of sable attacks on ermine. As the hunters noted, the sables only infrequently attack ermine. Thus, over a period of more than 30 years of commercial hunting, individual respondents mentioned only one to two cases of sable attacks on ermine caught in traps. This is likely due to the varied diet consumed by sables, including rodents, grouse (Tetrastes bonasia , Lagopus lagopus , Lagopus mutus , Tetrao parvirostris ), elfin cedar nuts and blueberries.

A sharp decline in the procurement of ermine pelts in Yakutia has been recorded since 1970 and is apparently associated with a reduction in the number of the animals. Thus, according to Kuzyakin et al. (1989) , the post-hunting ermine population in the country was in the range of 800,000 animals in 1981, 500,000 animals in 1982, 550,800 animals in 1983, 600,000 in 1984 and 800,000 in 1985. From 1995 to 2003, the post-hunting number of animals according to the Department of Biological Resources of the Ministry of Nature Protection of Yakutia ranged from 186,000 to 630,000 individuals, with maximum values recorded in 1995 (630,000), 1996 (570,000) and 2000 (420,000), and the minimum numbers noted in 1997 (254,000), 1998 (186,000), 1999 (243,000), 2001 (287,000), 2002 (195,000) and 2003 (220,000). The post-hunting number (March–April) of ermine in Yakutia in 2010 ranged from 215,000–220,000 animals, i.e., in comparison with 1981, the number was reduced 3.6-fold, and the post-hunting number of sables for this period (Sedalischev, 2012 ) had doubled (to 100 million compared with 200,000 animals).

It should be noted that, during the period from 1825 to 1857, when the sable population was low, the number of ermine pelts procured in Yakutia in some years were also reduced by up to 4-fold (Table 4 ).

Table 4. The exportation of ermine pelts from Yakutia in 1825–1857 (according to Diakonov, 1990 ).

Year	Annual average, units	Maximum		Minimum
		Quantity, units	Year	Quantity, units	Year
1825–1830	20,833	25,000	1825	18,500	1830
1837–1842	56,666	100,000	1839	25,000	1837, 1838
1850–1857	25,833	40,000	1851	14,000	1850

It is possible that the ermine population decline during the period from 1825–1857 was associated with an infestation of Skrjabingylus . According to Lavrov (1944) , Skrjabingylus disease can have a significant impact on the ermine population dynamics under certain conditions.

Based on an examination of 1167 ermine skulls, only 222 skulls were affected by the Skrjabingylus nasicola (Leuckart, 1842) nematode. The total intensity of infection was 19.0%. The age and sex differences in nematode infestation of the animals were identified, and it was found that the infection rate of males was 2.3 times higher than of the females, and infection rate of young animals was 1.7 times higher compared with that of adults ( Table 5 ).

Table 5. Skrjabingylus nasicola nematode infections of ermine in Yakutia.

Region (areas)	Examined/infected (%)
	Total	Adult	Young	Males	Females
Northeast Yakutia Verkhoyansky, Mid-Kolymsky areas	366 134 (36.6)	135 52 (14.2)	231 82 (35.5)	252 95 (25.9)	114 39 (10.6)
Western Yakutia Viluysky, Verkhoyancky, Kobyaisky areas	191 7 (3.6)	71 2 (1.0)	120 5 (2.6)	128 4 (2.1)	63 3 (1.6)
Tundra zone Nizhnekolymsky, Bulunsky areas	97 30 (30.9)	38 14 (14.4)	59 16 (16.5)	75 22 (22.7)	22 8 (8.2)
Central Yakutia Namsky, Khangalassky, mountainous areas	513 51 (9.9)	179 13 (2.5)	334 38 (7.4)	358 34 (6.6)	155 17 (3.3)
Total	1167 222 (19.0)	423 81 (6.9)	744 141 (12.1)	813 155 (13.3)	364 67 (5.7)

Ermine from the north-eastern regions were the most commonly affected by this nematode. For the six hunting seasons from 1983/84 to 1989/90, the rates of infection of the animals caught in the Srednekolymsk area were high, at 87.5% in 1983/84, 86.5% in 1985/86 and 83.7% in 1986/87. It should be noted that stoats caught in Western and central Yakutia, compared with individuals from Northeast Yakutia, were affected by the Skrjabingylus infection to a lesser extent. For example, for the three fishing seasons, the nematode infestation rates of animals were 20.0% (1971/72), 26.6% (1972/73) and 58.4% (1973/74).

Thus, with the increasing number of sables, a gradual ousting of ermine from the ecological communities of the taiga occurred. This process was accelerated during times when there was a smaller number of forest rodents and a limited crop of the main taiga feed. In such years, when both competing species are starving, the probability of sable attacks on ermine increases. Nevertheless, the impact of sables on the number of ermines is relatively small.

The total nematode infestation rates of stoats caught in western and central Yakutia, compared with individuals from northeast Yakutia is insignificant, and it is likely that this parasite did not significantly affect the number of these animals in these two regions of Yakutia.

During the studied period (1970–2010), along with a decrease of the ermine population, in some years, there was also a significant decline of interest from hunters because of the low purchase price of their pelts. In the western, north-eastern and central regions of Yakutia, hunters switched to procuring muskrats and sables as the most profitable fur animals. This may have contributed to changes in the populations.

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